What's the worst movie you've seen and why?

Keep in mind this is not a place to just bash a movie--tell us why the movie in question is bad without giving too much away (for those that may still want to watch the movie).

As for me, the worst movie that I've seen was The Master of Disguise--the story had potential, but horrible characters and stupid jokes dragged it down--you know you're in trouble when your hero is named after a nut.