I gotta say that my favorite main character in FF... Well, let me rephrase that. It's a two-way tie.

1.) Firion
~What's not to like about him? Really, as a character, this guy's a rather stable and capable individual. Sure, he's a rebel army reject like the rest of them, but I can really find nothing to hate about him. He doesn't stand out, but has a subtle stlye to him. That is, compared to the likes of other Final Fantasy heroes. Besides, the scene with him and Lamia Queen is just plain priceless. *lol*

2.) Guy
~First off, every time one encounters a chatacter named GUY, I've come to find that 100% of the time, the character is just plain awesome; The notable examples being Tales of the Abyss and Street Fighter Zero/Alpha. If you disagree, this one line will say it all...

"Guy speak beaver."