Revealing mistake: Close to the end of the film when Joe is in the woods with all the bad guys, he starts to shoot them, as he shoots the first bad guy, if you pause it before he shoots, you can see that there is a rather large lump in the guys forehead where he gets shot, obviously some kind of squib or something to make the effect of being shot in the head. (01:13:30)
Revealing mistake: After Hollenbeck has been tasered and dragged unconscious to the bad guys car, they open the door to put him in and lift him. Hollenbeck uses his right leg to step forward.
Revealing mistake: This is when Joe finds out his wife is cheating on him and shoots their wedding photo. If the bullet hit the photo, where is the bullet hole? It shows that something other than a gun was used to destroy the frame in this shot. (00:16:40)
Revealing mistake: When Mike Matthews' car explodes, it's a dummy in the car, not a person.