I was actually contemplating something like this the other night. The answer for me would definitely be a parrot of some kind. I don't know what kind, don't necessarily care what kind. Could be a macaw, a cockatoo, or even a parakeet...just some kind of parrot. I think I've always wanted to be some kind of bird, and parrots are the most fascinating to me, mostly because of their intelligence and their beauty.
Also I'm thinking with their mimicry and talking skills, I could still communicate to people in some way. :P