All Characters have their good points.

Zidane: A Thievery that does 9999 damage and the all powerful Dyne ability.

Dagger/Sarah: Eidolon POWER!!!

Eiko: Eidolon Power + Double White Magic + Full Life + Esuna + Holy

Vivi: DoomsDay and Focused spells.

Quina: Magic Hammer, Matra Magic, White Wind(Which can go through reflect), Auto Life, Angel's Snack, Lv5 Death(Quite useful against Grand Dragon's if you want EXP quickly), Mighty Guard and Bad Breath.

-Oh, if you wanna get Quina to eat, try using Matra magic (reduces enemy's HP to 1) and then devour them. (Of course, to learn Matra magic you gotta eat a Zaghnol first )

Amarant: Chakra and Aura

Freya: Rei's Wind and Dragon's Crest which deals 9999 damage. Jump...Maybe.

Steiner: Shock!