Umaro, Gogo, Gau, Mog, Red XIII, Quina, Kimahri, or Fran

I felt all of those were out of place except for Red XIII and Kimahri.
However, Umaro, Gogo & Mog never bothered me (I think) because
a) they were just side characters
b) the difference between them an the game style was a lot less stark. Should they remake this game with updated graphics I think I would take more issue with them.
Quina I hated with a passion, I couldn't wait for every scene he/she was in to end. (I seem to remember it's she, but not sure.)
Fran, and the Vera in general didn't fit the game to me, just a hold over from FFTA they were forced to include. (And probably some T&A to help boost some game sales.)
Had there been no Cosmo Canyon I don't think Red XIII would have bekonged, but by adding such an element into the word it is easy to see his place.
Kimahri didn't really have a lot to add to the story, (I could also argue that no one in FFX did ), but I felt stylistically he fit right in with the world of Spira.