What fish can I have in a 10 gallon fish tank?

You are limited with a 10 gallon. 3 platies could work, they are hardy, colourful and even the males are rarely aggressive towards eachother. Guppies can sometimes work in a 10, but ideally need a 20. If you did only females and stuck to 3 or 4 that would work, but if you do all males you would need more of them to spread out agression so would need a bigger tank - at least a 20. For the bottom some dwarf cories or a group of kuhli loaches would work but that's about it. You would need a sand bottom for the cories/loaches though so keep that in mind. Gravel will eventually damage their barbels making them prone to infection.

I would avoid tetras, even little ones like neons. Firstly, neons are very sensitive fish - not hardy at all. But any schooling fish does need room to swim and a 10 gallon just wouldn't cut it. I would stick to a few platies and a few bottom dwellers as I mentioned above. If you heavily planted the tank it would look pretty awesome :)

Cardinal tetra neon, catfish, loache, head and tail light, rasp boar.

I cheat in my bedroom tank, I technically have it overstocked with fish. I have a deal with our local 'fish and more ' store. I buy the teenie juveniles and will have about 20 in the tank and keep them until they hit about 3/4 inch or so. I have a custom 15 gallon that's long and taller but narrower than most tanks. It was made for raising plants but I received it as a gift from a friend.

When my fish are close to average adult size I bring them back to the store, trade them for food and more young fish. I always have a catfish I the tank but the different species change pretty often. Angel fish or silver dollars, kissing gromets would be a tad big for a 10 gallon.