How can anyone possibly say Gogo is bad? Here's my favorite attack sequence:

1. Someone Quicks Relm.
2. Relm casts Ultima 4 times (with Gem Box/Economizer).
3. Gogo mimics.
4. BOOM!

Umaro is just awesome, too. He's random, but really, really strong. He's especially fun in the Colosseum.

My least favorite character is Strago. I'm way too lazy to get him any decent Blue magic besides Grand Train.