1. Psycho (1960)
This is obviously Alfred Hitchcock’s original film, although some of the remakes were fair. Psycho pushed the envelope for what a horror movie could do, get away with, and succeed with from an artistic standpoint. Making the bold choice of killing off its starlet, Vera Miles, early on (which started the trend continued by films like Scream), Psycho invented the slasher genre in a big way. The twist ending still holds up after many years of repeat viewing.