Leader: Paladin Cecil, pure power and has the perfect leadership qualities.
Damage Caster: Terra, she is a natural and powerful spell caster.
Healer: Aeris, the Great Gospel limit break can become useful in tight spots.
Ranged Fighter: Edgar, spears and tools, baby!
Melee Fighter: The Knight from FFI, absurd amount of power and great defense to back it up!
Wild Card: Yuna in the Lady Luck Dressphere, it always worked wonders for me in FFX-2.