There are lots of choices even for a little 10 gallon!

If you want to go with a betta you will have to try and find a mellow one. Not all bettas get along with other fish. Three or four cory cats would do well with one betta. Or three or four Oto Fish. Oto fish are small algae eaters and cory cats are small bottom feeders. For way more information may I suggest www.petfish.net/forum