Male Kenyan sand boas (and maybe smallish females), Western hognose snakes (those are the two I own), male rosy boas, I think maybe some garters (not sure), ringneck snakes, rough green snakes... and anything else that stays around 16-18 inches or less, given that a 10 gallon is 24 inches long and you're sticking to the '2/3 rule'. The world's smallest snake is an adult at four inches and probably could live in a sugar dish. But it's a blindsnake that eats ant larva. The world's smallest venomous snake, the Namaqua dwarf adder, is very cute. I thought I'd toss that in.