"Plan 9 From Outer Space" is the hands down winner. Anyone who isn't voting for it, has not seen it. There is no possible movie that was dumber. "Dumb and Dumber" set out to be stupid and suceeded. Plan 9 was actually a serious attempt at a movie.
If you can't find it to watch at the video store, get "Ed Wood" starring Johnny Depp. It is about the making of this movie.
Imagine a director so down on his luck that he makes a science fiction movie about vampires with a ridiculously low budget. Then imagine an actor so down on his luck that he agrees to star in it. That director was Ed Wood. That actor was Bella Lugosi. Lugosi died during the making of the film and for the rest of the movie, his character is played by someone else holding a cape over their face.
Trust me...