When I compiled my list of "scary non-scary movies," I neglected to add the most horrifying film of all time: The Peanut Butter Solution. Thankfully (or, perhaps not), a commenter reminded me. Don't believe the happy trailer: nightmares FOREVER, crew.
If you remember this movie, you understand the horrors. If not, let me just say this: the movie involves a haunted mansion, a creepy art teacher, kidnapped children forced to make paintbrushes, and a scene that involves pubic hair that won't stop growing. I have vivid memories of the film from my childhood, including a scene where a bald boy's wig is torn off mid-soccer game, much to the amusement of his fellow players, who mercilessly tease him. Wikipedia quickly reminded me of the rest, and now I won't sleep for years.
The Peanut Butter Solution [Wikipedia]