I don't ignore a lot of characters because I like variety and I also like keeping people's levels high.

VI - Gau and Setzer usually ride the pine in Kefka's Tower. Gau because he sucks and Setzer because I'm not a big fan of the Slot skill.
VII - Cait Sith. His limit break can get you a game over and that's dumb.
VIII - they all sucked
IX - Garnet. Eiko could do everything she did and better.
X - Kimahri. Jack of all trades doesn't work in a game where you can switch characters on the fly.
XII - Penelo and Vaan were kind of just 'there'.
XIII - Sazh, Snow, and Vanille were left out of my team down the stretch.