I have a betta in my 55, he lives with some bala sharks, guppies, platys, um....gouramis (2 kinds, one of each, an opaline and another one whose breed I do not know) a clown loach and a couple of plecs.
before that, he was in my 42 with a ceverum, fw flounder, and horsefaced loach. the ceverum nipped at his frilly fins so I eventually had to move him to the 55.
I tried a betta in my 10 gal frog tank, but they are small enough that a large frog (like mine) can and will eat them.
IMO a Betta goes great in any community tank, I would be weary of adding one to a tank with aggressive fin nippers though.
fern