Most memorable NPCs outside of main scenario or sidequests?

[Rocl]

Actually she doesn't remember all 1.0 players, only those who specifically had the Legacy storyline (that is, they completed the Lunar Transmitter battle in 1.0 and is therefore designated as one of the 'original' Warriors of Light) - she treats any other 1.0 player exactly the same as a new adventurer just newly woken to the Echo. I know this for a fact as she didn't respond in any different way to my character who I transferred from 1.0 (and which I never did the 7th Umbral Era story for, thus I did not get the Legacy storyline in ARR), she just acted like she had never seen Enki before.

Either way, it seems in Minfilia's case it wasn't that the Echo 'protected' her from the amnesia, more she used the Echo to view that character's memories and saw who they were. But again because I didn't get the Legacy storyline in ARR I'm not certain of exactly what it is she said to a player who had the Legacy storyline, instead having to rely on secondhand info, so take that with a grain of salt.

Ah, this I can tell you. When remeeting Minfilia at the Waking Sands again, she pulls you aside and tells you that the rest of the Scions (and most of the world) has forgotten you. She doesn't know why, but she asks you not to say anything. (Tataru mentions you seeming familiar, but I'm not sure if that's Legacy dialogue off the top of my head. Though she does find your name in her logbook? She doesn't fuss about that at all though, and it could be her writing it down)

Minfilia, Scions of the Seventh Dawn MSQ:

After five long years...you've come back to us, just as Louisoix said you would...
Words cannot describe the joy I feel at this moment. Welcome home.
Aye, I remember you still, and everything you fought for. Know that you are not entirely forgotten.
If Louisoix is watching us, as I choose to believe, he may now rest in peace, his mission finally fulfilled.

Minfilia, A Wild Rose by Any Other Name MSQ:

Forgive me for treating you as a stranger. I know you deserve better than this, considering all you've done for the realm.
It remains unclear why no one remembers you. We can only assume that it is a consequence of the power that Louisoix invoked to save your life.
But irrespective of the cause, know that whatever shroud has fallen upon people's memories, there will surely be a way to lift it.
Thank you for understanding.

Cid, Lady of the Vortex MSQ:

Cid: It took a while for the memory to return, but I remember you.
Cid: The floating isle, van Darnus... We ended it, that day─or so we thought.
Cid: Listen─let's keep this between the two of us, for the time being.
Cid: If word got out that one of the Warriors of Light had returned, the eyes of the world would soon be upon us─our enemies' included. And that's the kind of attention we could well do without.
Cid: What, isn't it enough that I know the truth?
Cid: Don't worry. A man of your talents won't go unnoticed for long. Someday, they will remember you─and you'll never know another moment's peace!
Cid: There, up ahead! Ready, old friend?
Cid: Hah! Some things never change! We're going in!

In this case, I'd said us using the Echo to help him unlock his memories pierced the shroud of amnesia as well.

There isn't much other dialogue I can recall until The Ultimate Weapon MSQ:

Minfilia: Please, Mother Hydaelyn. Please light his way through the darkness...
<flash of light, blue streak across the sky>
Y'shtola: It's him. I feel his presence!
<flash of light, blue streak across the sky>
Yda: Can it be─? Is it really him!?
Papalymo: I knew it! I knew it all along!
<flash of light, blue streak across the sky>
Kan-E-Senna: Who speaks...? The Crystal! She calls to us!
Merlwyb: I hear Her! The voice of Hydaelyn Herself...
Raubahn: She speaks of...
Strike me down! No wonder he seemed familiar! he's one of the Warriors of Light!
Raubahn: What are you smirking at, Cid!? You knew, didn't you!?
Cid: Oh, you mean our adventurer friend? Did I forget to mention he was one of the Warriors of Light?
Cid: Saved Eorzea, you know. Twice.
<Minfilia cries>
Minfilia: The shroud is lifted. They remember you...

I don't recall much other Legacy text in the MSQ, but I'm quite sure there's some sprinkled throughout. The next big thing I recall is Alisaie knowing you slew Nael van Darnus and Nael Deus Darnus knowing you killed the mortal vessel at Rivenroad as well. Given Deus Darnus' ambiguous status as "aetherial shade / simulacrum" we might be best to assume immunity to memory warping techniques. (I would say as a consequence of being Tempered, we know one with the Echo can't be Tempered, so one Tempered shouldn't be able to receive the Echo.)

After Final Coil Urianger does offer a theory for why the world forgot you:

Urianger: And though the veil hath been lifted from many and more mysteries, the haze which shroudeth the people's memory of the Calamity yet eludeth explanation. I have but half-formed theories, which I would share with thee, if thou art willing to listen.
Urianger: As thou knowest full well, when the combined might of the Twelve failed to contain Bahamut, Master Louisoix mustered what strength remained to him and sent you and yours beyond the reach of space and time.
Urianger: From his final words to the Antecedent, I doubt not but that he intended this from the first.
Urianger: 'Tis my belief that he invoked the power of the Keeper, and sent thee to a place outside of time, beyond the reach of the primal's wrath. Taken whence thou rightly existed, thou didst leave behind a rent in the fabric of reality.
Urianger: At the selfsame juncture, Master Louisoix struck down Bahamut, thus triggering the realm's dramatic regeneration. The occurrence of these events in rapid succession, I theorize, gave rise to the people's clouded recollection of the Calamity.
Urianger: Five years from that fateful day, thou didst return to us, to once again become Eorzea's valiant blade. Though my beloved master is gone, his hopes and dreams live on within thee, Warrior of Light.

That said, he doesn't offer up why some people remembered you. I'm unsure of what "half-Legacies" like Enkidoh experienced, as a consequence of only getting the "full-Legacy" experience (I'm not really sure how to differentiate the two, sorry). Was there the benefit of the altered opening (teleporting in at Snakemolt, the stone of Althyk's new location) or just the mostly out of character bonuses? (Reduced sub fee, goobbue mount, dated items, tattoo, etc.) I suppose if it's the latter, it might be safe to assume even though the character simply didn't canonically develop the Echo until after the Seventh Umbral Era. A bit boring and lame, but as with most things in an MMORPG story regarding your player character, something easy to fudge for your own headcanon/RP purposes. If Louisoix did teleport you away as well, then I've got nothing.

I do feel it important to point out it's doubtful Minfilia used the Echo on you, as she specifically bemoans not being able to control the Echo in the very quest you're introduced to her.

In short, the Echo is a truly extraordinary power. And this power is strong within you.
It is only a shame that we cannot use it whensoever we choose.
That's right. I too possess the Echo.

(She explains this to you even if you're Legacy, and in 1.0 you definitely had "Use the power of the Echo?" prompts which seemed an awful lot like choosing when to use it but I digress.)

If it wasn't for Rostnsthal, Warburton, and some others I'm likely forgetting, I would write off all the "original 1.0" storyline as non-canonical/retconned. (That is, anything pre-Yoshida/7UE) It just seems that should you not be a Legacy player, these events still happened just without a meddling time-hopping greenhorn adventurer.

The next big thing is the curtain of amnesia over Hydaelyn's citizens lifted all at once? I'm not sure, I think I recall other minor NPC dialogue changing, but I have nothing concrete. F'hlaminn, I don't think, has any extra dialogue should you have been an Ul'dahn Legacy player, for example. How did Alisaie (and Alphinaud, who furnishes her with the information) know that you slew Nael van Darnus? Was it some record kept in a book somewhere? Did Alphinaud know who you were the whole time? I don't think we have answers for this.

Likewise, I can't think of another Echo-blessed character we've met in both 1.0 through 3.0 so far other than Minfilia. I don't think it's a stretch to assume the Echo was somehow involved in her memory preservation though. I think Una Tayuun might've been the Echo user in her party, but she suffers from some degree of memory loss as well. She has a strong inclination she was a Scion, but they weren't called Scions back then.

Why don't any o' these blokes know who I am!? I swear I was one o' 'em Scions o' the Seventh Dawn!
Only we didn't have such a fancy name back then, an' the headquarters was in a far more convenient location.
At least, I think it was... Or is me mind playin' tricks on me? Gods, what's wrong with me? Why can't I remember it more clearly?

I can't recall which of those lines is "Legacy" only, if any are. But in the five year time skip she also appears to have developed quite the accent as well. The other two, best I can recall, you can't even interact with. Speaking of hazy memories, I swore she had a bit of dialogue about Tataru finding her names in the Logs but I can't find it flipping through these notes and files and tables...

[Tenkuu]

Actually she doesn't remember all 1.0 players, only those who specifically had the Legacy storyline (that is, they completed the Lunar Transmitter battle in 1.0 and is therefore designated as one of the 'original' Warriors of Light) - she treats any other 1.0 player exactly the same as a new adventurer just newly woken to the Echo. I know this for a fact as she didn't respond in any different way to my character who I transferred from 1.0 (and which I never did the 7th Umbral Era story for, thus I did not get the Legacy storyline in ARR), she just acted like she had never seen Enki before.

Either way, it seems in Minfilia's case it wasn't that the Echo 'protected' her from the amnesia, more she used the Echo to view that character's memories and saw who they were. But again because I didn't get the Legacy storyline in ARR I'm not certain of exactly what it is she said to a player who had the Legacy storyline, instead having to rely on secondhand info, so take that with a grain of salt.

Oops sorry, I meant to say that it was only Legacy players, totally forgot that, my bad. However, I disagree with the idea that she used the Echo to view your character's memories. Not only is there no indication of this being the case, but viewing someone else's memories that you yourself don't remember would mean nothing to you.

[Tenkuu]

There isn't much other dialogue I can recall until The Ultimate Weapon MSQ:

I've watched the videos of a Japanese girl who was a 1.0 Legacy player. She started in Ul'dah, and Thancred, upon your first meeting with him, asks you whether the two of you have ever met before, but then appears to dismiss the feeling by saying that he was just feeling nostalgic and seems to have mistaken you for someone else. From what I hear, various other NPCs have little reactions like these, but nothing on the scale of Minfilia's.

I don't recall much other Legacy text in the MSQ, but I'm quite sure there's some sprinkled throughout. The next big thing I recall is Alisaie knowing you slew Nael van Darnus and Nael Deus Darnus knowing you killed the mortal vessel at Rivenroad as well. Given Deus Darnus' ambiguous status as "aetherial shade / simulacrum" we might be best to assume immunity to memory warping techniques. (I would say as a consequence of being Tempered, we know one with the Echo can't be Tempered, so one Tempered shouldn't be able to receive the Echo.)

That's very interesting, could you ever post the dialogue where Alisaie and Nael say those things? I'd love to compare them to my own non-Legacy status.

That said, he doesn't offer up why some people remembered you. I'm unsure of what "half-Legacies" like Enkidoh experienced, as a consequence of only getting the "full-Legacy" experience (I'm not really sure how to differentiate the two, sorry). Was there the benefit of the altered opening (teleporting in at Snakemolt, the stone of Althyk's new location) or just the mostly out of character bonuses? (Reduced sub fee, goobbue mount, dated items, tattoo, etc.) I suppose if it's the latter, it might be safe to assume even though the character simply didn't canonically develop the Echo until after the Seventh Umbral Era. A bit boring and lame, but as with most things in an MMORPG story regarding your player character, something easy to fudge for your own headcanon/RP purposes. If Louisoix did teleport you away as well, then I've got nothing.

I personally consider that in canon, all current Warriors of Light are supposed to be 1.0 heroes returned. Several small elements seem to imply it. And rather than not developing the Echo until after the Seventh Umbral Era, it is probably just that your non-Legacy (or half-Legacy) character was one of the many ordinary members of the Path of the Twelve and never did anything extraordinary, including going to Carteneau. I believe it was Anonymoose who posited that theory, though I could be wrong.

(She explains this to you even if you're Legacy, and in 1.0 you definitely had "Use the power of the Echo?" prompts which seemed an awful lot like choosing when to use it but I digress.)

Those prompts sound more like they were there solely for you the player, not you the character. Ie, the scene was going to pull your character into an Echo whether you liked it or not (in order for you to progress), but wanted you the player to be able to choose when to start the Echo. Kind of like how instanced battles don't start on their own when you reach and interact with a destination, but instead ask you to confirm that you're ready to start the fight.

The next big thing is the curtain of amnesia over Hydaelyn's citizens lifted all at once? I'm not sure, I think I recall other minor NPC dialogue changing, but I have nothing concrete. F'hlaminn, I don't think, has any extra dialogue should you have been an Ul'dahn Legacy player, for example. How did Alisaie (and Alphinaud, who furnishes her with the information) know that you slew Nael van Darnus? Was it some record kept in a book somewhere? Did Alphinaud know who you were the whole time? I don't think we have answers for this.

Likely Alphinaud and Alisaie know this information from Louisoix's journal. Otherwise, Urianger is known in the Tales from the Calamity to have kept a correspondence with them, periodically sending them letters to keep them updated on the situation. If not through this correspondence, Urianger likely simply told them about it in person.

Likewise, I can't think of another Echo-blessed character we've met in both 1.0 through 3.0 so far other than Minfilia. I don't think it's a stretch to assume the Echo was somehow involved in her memory preservation though. I think Una Tayuun might've been the Echo user in her party, but she suffers from some degree of memory loss as well. She has a strong inclination she was a Scion, but they weren't called Scions back then.

As I understand it, Una's case is not so much amnesia as it is her feeling like she's going crazy because she remembers being part of an organization where no one remembers her. She is probably doubting her own memories as a result.

I can't recall which of those lines is "Legacy" only, if any are. But in the five year time skip she also appears to have developed quite the accent as well. The other two, best I can recall, you can't even interact with. Speaking of hazy memories, I swore she had a bit of dialogue about Tataru finding her names in the Logs but I can't find it flipping through these notes and files and tables...

I don't think any of them are, I think everyone gets them. I think the more specific Legacy lines all relate to you in some way, whereas here Una is just sharing her own thoughts with you.

[Rocl]

There's a lot to reply to so I'm just gonna focus on the Coil dialogue you asked about first, it started in Second Coil but there were flags in Final Coil - Turn 3 after that:

Given I don't really know what is and isn't Legacy for this first bit, I'm going to bold what I think is the Legacy dialogue. These can be pretty lengthy, so I'm going to truncate them to the relevant bits.

Second Coil of Bahamut - Turn 2 CS1:

Alisaie: That armor─ No, it couldn't be!
Alisaie: Be on your guard, Rocl! Though it defies all reason that he should live, you must surely recognize that armor.
Alisaie: It belonged to the Black Wolf's equal. The legatus of the VIIth Legion.
...
Nael deus Darnus: This blessed sanctum is the domain of my god and His beloved children. Seek to defile its glory, and you will answer to me.
Alisaie: How is this possible? Alphinaud told me of Nael's final defeat at your hands.
Alisaie: Whatever the truth of the matter, we must be on our guard─there can be no reasoning with the worshipers of a primal.

Second Coil of Bahamut - Turn 4

Alisaie: That...that surely cannot be Dalamud!? How─ Where are we!?
Nael deus Darnus: Your companion knows this place well. For it was here that he slew Nael van Darnus.
Nael deus Darnus: This is a grave for the undeserving.
Nael deus Darnus: And for the crime of trespassing upon my god's sanctuary, this place shall serve as your grave too!
...
etc

The Final Coil of Bahamut - Turn 3, CS3:

...
Louisoix: But Bahamut would not be caged by such feeble bars─too vast was his might; too fierce his rage.
Louisoix: You know of what happened next. I used the last of my strength to send you and your companions outside of time, and then prepared to meet my end.

The Final Coil of Bahamut - Turn 3, CS5:

Louisoix: Whether it be for man or for dragonkind, the question of justice is irrelevant. The elder primal will leave naught but a smoldering wasteland for both his children and ours.
Louisoix: I beg you to defend Eorzea─as you always have, and as I always knew you would.
Louisoix: This portal will take you to the final internment hulk. 'Tis time for the tale of Bahamut and his part in the Calamity to come to an end!

I can't recall any others, and they're very minor line additions/alterations but man if they didn't make me feel like a real badass Warrior of Light in two different Astral Eras.

[Grayve]

Osaulie was the girl I was talking about earlier. She has her own quest. http://ffxiv.gamerescape.com/wiki/Unfulfilled_Dreams

It still makes me sad.

[Mysterysword]

Wilred's story sticks with me the most. He almost gets tricked into summoning a primal/god, reforms, sets out from Little Ala Mhigo to join the Crystal Braves and do some honest work, and gets murdered for trying to do the right thing. It's a pretty brutal reminder of how cynical Eorzea can be at times.

But, all this takes place within the MSQ, so for other examples.

I would say one of the most memorable NPCs is the man and his son, in the hallway to the airship landing in the Gold Saucer. The boy is saying how he doesn't want to work in the silver mines, and the man is saying that it'll "only be for a few moons", and then his debt will be paid. So basically, we have child slavery paying off a debt that was probably accrued due to a gambling addiction.

From the job questlines, there's Zhai'a Nelhah, for proving that male Keepers actually exist(!) and for being a strangely idealistic example of a character that starts out as xenophobic and narrow-minded, eventually learning to see past his upbringing and benefiting from a changed attitude.

(I seriously cannot recall off-hand, even a single other male Keeper NPC that I can talk to.)

There's also Karasu, who I found pretty annoying and cliché at first, but then turned out to be way more self-aware than I gave him credit for, which was interesting.

[Morningstar1337]

Does the Job/Class quest count as sidequests? I did find the Crafting quests to be memorable, particularity WVR

[Berethos]

There's also Karasu, who I found pretty annoying and cliché at first, but then turned out to be way more self-aware than I gave him credit for, which was interesting.

I found him insufferable at first...

But by the end, he managed to become one of my favorite job quest NPCs so far.

And, since I rerolled to this character and plan on getting everything to 60 on them (eventually), I get to go through his stuff again.

[Laili]

Gena might be the only person in all of Eorzea that doesn't worship the WoL, so I give her points for that.

[seekified]

Stephanivien (MCH questline). I really enjoyed the MCH quests for their larger view on Ishgard's politics and class divisions, and Stephanivien really strives to make the "normal people" worth something, and give them strength.