I'd have to say Spacehunter: Adventures in the Forbidden Zone. It's a dog ... it's silly, cheap, badly acted and a ton of fun. Molly Ringwald (the year before 16 Candles made her a star) is hysterical, or obnoxious, or both depending on your point of view. Michael Ironside is having way too much fun to be in this movie. Ernie Hudson is doing the same part you have seen him do time and time again. The effects are laughable, the creatures are silly. It's marvelous. I think I may subject the WSPA to it this weekend (yes I do own it). OH, it was in 3D in the first run. What else could you want from a bad movie?
So, own up.