I usually use people I cant stand, just for their limits. And, well, if I only used characters I liked, it'd just be Quistis the whole time. Squall is great for his Lion Heart limit, and Rinoa for Angelo's Invincible Moon. It's perfect for keeping Squall at low health for a good amount of time without him dying. Third is usually Quistis, mainly for curing and helpful spells, I dont use anyone else's limit breaks much.