Revealing mistake: Near the end, Clint Eastwood is sneaking up on a house at night. The old guy (Ed Begley Sr) shoots at Eastwood repeatedly until his gun is empty as Eastwood dodges from tree to tree. Just before running directly to the house, there is a strange black circle that completely covers Eastwood for a few seconds. It is very obvious and no reason why it should be there.
Revealing mistake: Towards the end of the credits, on the highest mountain peak, you will see an air traffic light flash twice.