A Nightmare on Elm Street (1984)
Long before Freddy Krueger became the slasher version of Gallagher, he was presented as one of the most ominous horror villains of all time. I don't like a whole lot of the sequels (OK, Dream Warriors is pretty good), but there's no denying that the original Nightmare on Elm Street still holds up as a remarkably scary movie. The late, great Wes Craven knew when a scary story should be light... and when it needed to fall into darkness. Elm Street is mostly the latter -- and that's part of why it works so damn well.