Hmm...

FFI: Garland
FFII: Minwu
FFIII: Desh
FFIV: Rydia
FFV: Gilgamesh (honorable mention Cid and Mid)
FFVI: Locke
FFVII: Cloud (honorable mention Sephiroth)
FFVIII: Squall
FFIX: Beatrix and Vivi (tie)
FFX: Auron
FFX-2: Rin
FFT: Agrias and Ramza (tie)
FFTA: Marche