Dabbling

I know its not generally acceptable to keep fish in a fish bowl as there is generally no filtration and the habitat is too small for most breeds of fish. My question is then what kind of fish may I keep in my bowl. It has to be a surface breather that grows no more than 2 inches and doesn't mind isolation.
I live in a dorm thats rules are you can have no pets, save for fish kept in no more than a 2 gallon bowl.