1) Psycho (1960)
Psycho is a masterwork of suspense and horror. In my opinion, murderous psychos don't get any scarier than Norman Bates. The shower scene has some of the most terrifying footage in movie history. I doubt that I'm the only woman who hesitates to check into a motel alone since seeing the film. My favorite line: "A boy's best friend is his mother."

2) Dracula (1931)
There have many movie adaptations of Dracula, but to my mind, nothing tops the 1931 classic starring Bela Lugosi in the title role. Of course, circa 1931 special effects don't match the visual wizardry of modern movies, but the eerie atmosphere this movie creates in my imagination is perhaps the most potent effect ever invented.

3) Frankenstein (1931)
This classic horror film based on Mary Shelley's novel is the monster movie that defined the genre. Demented by his power in artificially creating a man-like monster, Dr. Frankenstein is a mad scientist who exclaims "It's alive! It's alive!" moments after zapping a cadaver into a living monster. Boris Karloff's performance makes the monster seem pitiful and almost human.