Mythological creatures
I always thought a centaur (half human/half horse) would be cool, but I don't know how to create it. Maybe a full-sixed adult and a child or midget that wants to make some money working the back half?
There is another thread on here where someone wanted to know how to create a human/vulture hybrid (also known as a harpy). You should be able to find it through a search.
A minotaur would be neat. I have seen masks and costumes of it where it was identified as something else, but that's obviously what it is. The sellers probably figured that no one would know what a minotaur is. I think there was a recent horror movie with the same name that might give you some ideas for props/scenes.