When I was in college we used to have door prize contests at our parties. They were usually cute (first five girls in a hat get a free plastic cup), but they were often sexual (first blond bush gets fifty bucks).
One time we had a "shortest penis" contest. The prize was twenty bucks. Low and behold, no one wanted to enter. Toward the end of the night, a guy came up to me and my roommate and asked who won. When we told him no one had entered, he pulled down his pants, showed us was was probably a six inch flaccid and said "Then I guess I am the shortest. Where's my money?" We paid him on the spot.