For me, it's Roland Emmerich's 10,000 BC. It has 10% on Rotten Tomatoes, and it's based on a crackpot theory about the pyramids from the rear end of Graham Hancock. But somehow, no matter how many times I see this movie, I never get tired of it. The scene where Steven Strait javelins the Pharaoh and shouts "He is not a god!" is one of my favourite movie scenes ever. Also, the music is awesome, the filming locations are gorgeous, and the miniature pyramid models used in production are fantastic. So despite the story being illogical and stupid, and the historiography being absolutely batshit, 10,000 BC will always be one of my guilty pleasures.