Goodfellas (1990)

Revealing mistake: In the scene where Lorraine Bracco points a revolver at Ray Liotta's head, after Ray Liotta turns the tables and now points the gun at Lorraine Bracco as he gets up and walks away you can see Ray Liotta steps on Lorraine Bracco's hand and she opens her mouth wide like shes screaming but it must have been cut from the audio, as Ray walks off camera his expression changes to show that he knew he had accidentally stepped on his co-workers hand.

Revealing mistake: In the scene where Karen is too afraid to accept free clothes from Jimmy and speeds off, the yellow NY state license plate falls from the parked car to reveal the modern white one underneath. (02:11:35)

Revealing mistake: In the scene where Tommy gets fatally shot, his body falls to the ground. As it falls, you see his right hand wobble like rubber, making it clear it is a rubber dummy used for the scene. (01:51:30)