If you'll allow, I'll recommend two.
First there's Faust, a silent picture from 1926 made by F.W. Murnau (of Nosferatu fame). Great haunting imagery, spooky atmosphere with with eerie undertones. And a ever changing devil that is downright creepy a fair amount of times.
Also there's Curse of the Demon (or Night of the Demon, depending) which is this Dana Andrews picture from 1957. The demon is surprisingly well detailed in this picture and is rather ominous. Great sounds, great vibes.
