Alfred Hitchcock's Pyscho
Do you like staying in hotels? Do you like taking showers? Do you have an unhealthy relationship with your mother, to the point where you like to wear her clothes. If so, then this is the movie for you.
Arguably the first modern horror movie ever. Psycho sets the stage for so many other good horror movies to come. Personally, I am not a horror fan, but this is very tame for a lot of movies that are out today. It is truly a classic and should be watched at least once by all.