A female betta splendens can be just as nasty as their gender counterpart.
Betta enisae on the other hand are a peacefull betta. Male and female.
Gouramis are nice, just keep away from the three spot gourami, the blue and the yellow ones...they can be nasty. The dwarf gourami might fit inn, but no more than one male and one female.
Theres hundreds of diffrent tetras you could use, just make sure they can be in a 10 gallon, ,most need alot of space and a big group.
Corydoras species are lovely and friendly, and usefull..cleans up the filth at the bottom. Theres a pygmy cory you could keep.
Coolie loaches, make sure theyre a group or youll never see them =p
Black molly ?
But all in all i think you should concentrate on the bottomdvelling fishes. 10 gallon isnt much, and it gets easily overstocked.