In Jaws, the scene where Quint is eaten by the shark is edited out of order, so he has blood in his mouth, then no blood, then a huge explosion of blood, then no blood again. Also during the autopsy of the first victim’s remains, Hooper picks up the arm and says “so this is what happens”, but doesn’t follow it up with anything.

In most films I can see the tyre marks from previous takes where cars pull up in sand or dust.