I prefer the Smile-Tossing Jugglers, myself.

Two Jugglers (or any Moogle with Acrobatics as a secondary command) just spam Smile Toss at each other. It's essentially Quicken, making the target act instantly. Only it costs nothing. With the way Exp works in this game, you can just spam it back and forth between two Moogles for 10 Exp a round, and no one else will ever get to move. You can get to level 50 in a single fight if you're patient enough.