Back To The Future 2 - Moving Hand
When Marty is in 2015 and showing the kids how to play the arcade game (with the gun) watch carefully. When he first takes aim his left hand moves on top of the gun as he goes to shoot. However, when it cuts to a close up of the gun from behind, his hand is not there! The cut is instant so he couldn't have moved it.
The BTTF2 video
on 07-04-2000 and