A mouse! It sounds like your looking for something small, a mouse is perfect! They are very cute, i have a pet mouse myself their the best! You can find cheap ones at petstores, i recomend getting a feeder mouse, not only is it a good pet but you save it from getting eaten.
A rat! They are very cute, food is not expensive, and it is not a long term commitment because they only live 3 or 4 years. If you decide to do this though, you will need to get 2 because they are very social animals and need lots of companionship.
You should get a komodo dragon because you could take it to the park and say "Look at my dog. Isn't he the greatest?". Then, if other dog owners snub you, have your dragon eat their dogs. Let them snub you now.