I- The light warriors. The fact that they have literally no personality means they have no capacity to do anything annoying.
II- Guy. He speak beaver.
III- Eh, I dunno. Cid is pretty cool.
IV- Cecil. Just because.
V- Gilgamesh, thanks to the GBA localization. It's morphin' time!
VI- It'd be easier to list the ones I DON'T like, but Kefka rises above all the rest. I like Cyan too, for his backstory.
VII- Cid, Red XIII, and Tifa are the only characters I like at all, so I guess they get "favorite" status by default.
VIII- Irvine.
IX- Vivi.
X- Auron and Lulu.
XI- Myself. Since that probably doesn't count, Ajido-Marujido
XII- Basch.
Tactics- Cid
TA- Cid
TA2- Cid