The Omen is a classic movie from the 70's. I first watched it when I was 10 and didn't enjoy it. Four years later, I rent it, pop it in, expect nothing at all, and was blown the fudge away! :p

Agh, this movie had some pretty sweet kills too. The guy who got beheaded by the sheet of glass - brilliant. The woman who hung herself just after saying "It's all for you, Damien." Man, great stuff in this flick.