Plan 9 is supposedly the worst movie ever but I think it's kind of hilarious. A cop scratches himself with his own gun!
I think the last bad movie I saw was called Impact. A meteor hit the moon and changed the luna patterns around the world but then the moon started getting closer to Earth and apparently it's magnetic because all these cars started lifting up and junk? It totally ruined the theory of gravity and the characters were all like OH WHOOPS SCIENCE ISN'T THE ANSWER! I fell asleep after 3 hours but woke up an hour later and it was still on.