I have a betta, three ottos, and a really large cherry shrimp in a five gallon. Bettas have a lot of personality and recognize people in a certain manner.
I've also had puffers in the past, marked as figure eight puffers but I believe they're the same thing as Indian puffers. They have beaks, love other fishes' fins and are great snail control. Not much for a community tank I don't think. Maybe a species specific?