Black Christmas (1974):
It's a simple premise. A sorority house full of college girls are getting ready to head home for the holidays. But one girl goes missing and the rest are continually harassed through obscene phone calls and mysterious noises. We get out-of-control Margot Kidder--she is the best in this movie. Funny and beautiful. We get the drunk and hilarious sorority mom. There are some aspects of Psycho in here and a stalker boyfriend who can't take a hint. Bumbling cops...I can't believe this isn't more widely known. Classic. Go watch it!