Fast Times at Ridgemont High
In the iconic scene in Fast Times, one of the characters is daydreaming about Phoebe Cates climbing out of the pool in a red bikini and removing her top. If you were a teenage boy when this movie came out, it was probably on your most-paused list.
Psycho
The very last scene of Psycho is expertly done thanks to Alfred Hitchcock's directorial work. When Norman Bates is arrested, he looks right at the camera, and a human skull flashes over his face. If you pause at the right moment, the two images are superimposed in a terrifying way.