I like:

All jobs on 1 character.

So I don't have to pick one to main, I can just play them all! :3

Miqo'te.

They're just too darn cute :3

MSQ's

Very interesting and easy to follow (Unlike many MMO's where after about 5 minutes into the expansion it's basically "Things happened. Bad guys died. BUT NOT REALLY PREVIOUS BOSS OUT OF NOWHERE WHAM!" where half the time you're like "WTF am I even doing here?"). My only wish is that it could incorporate a bit more side content into the canon but I understand the barriers that prevent that (Inb4 retconning Crystal Tower raid into canon for ShB)

Items that stack up to 999

Even if you can only purchase/sell stacks of 99... Being able to go up to 999 is very nice and helps keep inventory more condensed (Y'all ever held on to over 2200 health potions in WoW? They only stack to 20. I had literally no inventory space ;_; Also, before anyone asks why I needed over 2200 health potions... It's like they say "Better to have 2200 health potions and not need them, then need 2200 health potions and not have them!"