Mog.
Two reasons: He's a frickin'
moogle for gorsh sakes. And he is cute. Very cute. Kupo!
Umaro and his Beskero behavior was alright, but in some situations you need control of all your characters. Shadow was an alright character, but he didn't get me going like the lil' guy over there. Setzer would probably be my second choice out of all the characters.
Who was the other one? Eh, he probably sucked anyway.