Corleone
Fish Herder
Corydoras, white cloud mountain minnows, african dwarf frogs... Everything comes down to the betta though. Some of them are more evil than others. Some can be kept in full community tanks - usually in that case, the risk is more to the betta than tankmates, as they're very vulnerable to nipping.
Some of my books advocate putting a male with many females - 6-10+, but nothing I've heard from people who have tried that makes me think it's a good idea. It might protect the females by dispersing aggression, but the male will probably still be on the warpath constantly.
Some of my books advocate putting a male with many females - 6-10+, but nothing I've heard from people who have tried that makes me think it's a good idea. It might protect the females by dispersing aggression, but the male will probably still be on the warpath constantly.