I: Matoya. She's hiding off in a cave nowhere near any towns in a room with talking brooms and chests full of drugs, not to mention having a stash of "Jolt Tonic" to give away to someone.
II: Leila. My God she saved me tons of times in Deist when the Hill Gigases had trouble hitting her.
III: Cid. The guy cracked me up every time he was on screen. Alwys fun to make him jump out of the room, too.
IV: Cecil. He's the only main character of the series that feels like one every moment of the game. He's exactly what a main character should be.
V: Lenna. A well intentioned character with a beautiful theme. She should have been the main character here. I would have said Butz, but ever since it got changed to Bartz, the buns puns can't be squeezed out anymore.
VI: Terra. A skilled, green-haired young woman that can just as easily kill things with a sword and torch them with fire spells? Yet she has a conscience underneath about doing it? Yes. great character.
VII: Yuffie. She's an easy-to-build one woman powerhouse. As soon as the sub is sunken, Yuffie can get a Conformer and Double Cut. Couple that up with 99 Hypers and limit level 1, and she's doing 6,000 damage a turn, while having an endless supply of healing.
VIII: Selphie. This is by default, though. The rest of the cast annoys me so much that she was the only one left.
IX: Zidane. I like everyone in this cast, so I might as well give credit to its leader. It helps that he can be really funny at times.
X: Rikku. I give her credit for managing to stay upbeat around unlikeable people such as Auron, Lulu, Wakka, and Tidus, especially after braving her fear of lightning.
XI: Verena. She married a goblin, then had to watch his flame flicker out.
XII: Balthier. He doesn't fall for any tricks. He doesn't back down when attacked and rarely causes the problem. Honorable mention to Penelo and Ashe.
XIII: Lightning. I had to pick somebody. lol
XIV: I haven't progressed far enough to pick yet.
XV: Iris. After hours of the same interchangeable four guys dressed in black, it was nice to have someone different. It's not that Iris was anything special, but compared to the main four, she was a breath of fresh air.