Having played...well pretty much all of them here is my list:
FF1: Fighter (seriously..mine hardly takes more than 1 point of damage!)
FF2-5: *shrugs. Didn't really care for those. They were good for the most part but the characters as a whole were bland, the only one that sticks out to me is Cecil from FF4 from this whole lot. This was still the early days of the series, though.*
FF6:
Sabin. Because he is just this awesome. This is probably my overall favorite FF character.
FF7: Cid
FF8: HAHAHA...no.
FF9: Vivi.
FF10: Auron. The only character in the game that didn't make me want to punch someone when they spoke. Such an awesome character was wasted on this horrible game.
FF10-2: *Tosses disc into open fire* This one shouldn't exist...
FF12: Own it...PS2 died before I could play most of it. I pass on this one.
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FFT: Ramza. Turn him into a monk and you might as well have created a GOD.
And since the game is awesome (And from the same company), I shall also throw in a bonus character:
Chrono Trigger: Robo.
(What I am trying to get at here is: Most of the FF series characters are horribly annoying, ESPECIALLY the ones in FF10. The series has generally gone downhill since the 16 bit era with a few that stand out, 7 and 9 being the notable ones. Six shall ever be my favorite, however.)