FFVI: Haven't finished it yet, but Setzer and Gau are pretty unreliable and therefore make place for some more dependable characters.

FFVII: Cait Sith. Love the character design, pretty useless in battle. Never used Cid much either.

FFIX: Quina, Amarant, Dagger. I lack the patience to learn Blue Magic, Amarant felt like a weaker Zidane and Dagger I just didn't like in general.

FFX: Played this game so much that during the storyline everyone appears at the frontline pretty evenly. Even Kimahri (TipAt first I always send him down Wakka's path. Kimahri's high MP makes him a more sustainable green mage than Wakka.). For most endgame stuff Lulu and Kimahri warm the bench, while Rikku's high agility is abused as first to switch out for Auron/Wakka. So she's sort of a benchwarmer too. Or a bait dummy. Something.

FFXII: All you ever need in this game is Ashe casting haste and berserk on Vaan, Balthier and/or Basch. No need for the Fran or Penelo.

FFXIII: Snow, Hope and Lightning. Didn't like them much and the rest does the job just fine.