Marcus in FFIX. He was playable temporarily, but I wanted him to stay so badly.

Like they said before, Alex in Golden Sun 2. It would have screwed up the story, but it would have been great.

Luzzu in FFX. Don't ask why, I just did. He was always one of my favorites in that game.

Biggs, Seigfried, Leo and Ultros in FFVI. I thought Sieg, Leo and Ultros were really cool/funny characters, and would be fun as permanent members. As for Biggs... I just wanted an Imperial soldier in my party.

I've got plenty of others, but it would take too long to write them. I always want characters I can't have in games.