I'm gonna throw some things out here (that while they should be pretty much common to their job, I don't see them often enough, which automatically gets my votes in a heartbeat). To better understand, these are the jobs I play (a lot).
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WAR DRK PLD
SAM DRG NIN
RDM BLM (sometimes smn)
BRD

1) DRK PLD WAR - Shirk -> If my MT or OT is in a tight spot dying (with CD's active or healers running out of mp from raises throughout the fight), and I provoke and they use shirk on me? BAM! Auto commendation. Cause not many players know this skill exists when tight spot issues come up in instances. And it helps me help them or others in the fight. I can't count the number of times I've seen bad places where the tank could've used shirk after I voke off them (but they still continue staying in tank stance while I'm in DPS stance the whole time).

2) SAM DRG NIN MNK - Goad -> If you goad ANY one player, either coming back from raise or running halfway into TP, that's automatic for me. You're part of the player base I can love and enjoy because you know what your tool kit has to offer. Also, I absolutely love you, cause I almost never see any competent toolkit users playing DPS outside of my FC and endgame linkshell (cross server).

3) RDM's or SMN's - Raise -> Anyone who helps prioritize raising people instead of dps (on an instance that doesn't really have any mechanics like 13min timer before auto wipes. Sure it extends the run a few min more, but getting the whole party back up and square one helps me as a tank the most since I'm keeping myself alive the whole time with CD's, and such)

4) RDM SMN BLM - Manashift - YOU GET A COM! AND YOU GET A COM! AND YOU GET A COM! EVERYONE GETS A COM! This is also something I don't see. As a BLM and a RDM doing anything, as I multitask quite often, checking party to see how we're doing on fights (24 man raids have this issue the most) where we have tons of mages in the party, and yet no one is using manashift except me. Healers having to ask for manashift. Big oof from me dawg.

5) BRD MCH (inb4DNC has same issues) - Refresh/Tactician - If I ever see this, that player is getting my commendation. My biggest pet peeve is doing anything (or not unless it's eureka which doesnt do much with people dying left and right) and a useless bard or mch who has no idea about their current skills to help support the party they're in.

If any one of these are done, that's an auto com from me. Cause I believe pigs will fly before I see players bothering to help support their party further in this game (until shadowbringers). I've seen just about everything, but I've seen an Elephant fly.