Movies where the main character is stupid but it's not a comedy.

I've seen many movies where the main character or characters is/are stupid and it's the cornerstone of movie's comedic nature; Naked Gun, Dumb and Dumber, basically anything Will Farrel and/or John C. Reilly play in.

Also I'm not looking for movies where people being unreasonably stupid is an excuse for bad plot; any slasher movie ever.