I don't really watch many movies, so the movie I'm about to list may not be the worst of all time, but it's bad:
Eight Crazy nights.
Seriously, the movie was terribly unfunny. Potty humor can be good, but not when it's extensively shoved down your throat. Then it's just gross. Not an inch of this film is worth a laugh, a chuckle, a chortle, a guffaw, a giggle, a cackle, a hee-haw, a snicker, a smirk, a titter, a whizgigging or even a "tee-hee". It's that bad.