Helter Skelter

I saw this movie a number of years ago, and it creeps me out to this day. Charles Manson, not only looks scary, but he doesn't seem all that attractive to me, so the fact he managed to actually get followers that would do his bidding is the truly scary part.

Charles Manson, one of the most notorious serial killers in history. The fact that he is still alive and has a parole hearing coming up in 2012 should be equally scary.

You can read more about him on Wikipedia.