Psycho (1960)

Revealing mistake: When Marion is driving her car through the night, she keeps looking at her speedometer. You can clearly see that the gear shift lever is in "park" as she is driving.

Revealing mistake: After Marion has been murdered there is a close-up of her face. If you look down to her neck you can see her pulse.

Revealing mistake: After Marion's sister and boyfriend look through the Number 1 bathroom and find the ring on the toilet, they turn off the light. On the wall behind them you can make out a square beam of light, but no other lights are on in the cabin.

Revealing mistake: When Marion's boyfriend and sister visit the Sheriff and his wife at home, there is a camera shot where you can see that the living room background scenery ends and there is no ceiling.