One of my favourite creepy films is the 1982 film John Carpenter's The Thing. I first saw it when i was about 14 or 15 and it freaked me out.
It's an unsual film as it has only a small 12 man cast, set in an antarctic research station,creepy music by Ennio Morricone and excellent (for the time)special effects.
It's also got a great ending, although not a happy one, with two main characters surviving at the end, both realizing either one of them could be the Thing.
Give it a go if you haven't seen it. Be warned though, it's quite gory in parts (keep the light on).
Man is the warmest place to hide!