I'm shocked so many people are saying Hope. Shocked.

Easily the most obnoxious character in the game, and easily one of the all time worst in the franchise. Please send him off to a deserted island with Quina, Zell, Selphie, and Irvine where they can all be obnoxious together. You can get a ticket for Snow while you're at it.

To answer the question, Fang. Although I did really like Sazh a lot, and Lightning was pretty cool. Vanille was kind of annoying at first, but she completely redeemed herself by the end. They all need to change their names, though. And should get on that right quick.