Ok, to some people this is stupid, but it cracks me up:
One day, a man hears a knock on his door. He opens it up and there's a snail on his porch. He picks up the snail and throws it as far as he possibly can.
10 years later, the man hears the same knock on his door. He opens it up and the snail is sitting there. He looks up at the man and says "What the heck was that for?!?"