Revealing mistake: After the sniper is shot he falls through the wall. Look at his silencer when he hits the ground - it bends where it attaches to the muzzle. A real metal silencer wouldn't do that. (00:41:25)
Revealing mistake: After Hank shoots Lou's wife in the kitchen, the camera shows Jacob walking into the house, then Lou's body on the floor with a puddle of blood around his head. If you watch closely, you can see Lou's left eye twitch.
Revealing mistake: When Hobbes is searching for information about Milano, he types his search into the webcrawler search engine and it takes him straight to the front page of the newspaper that is reporting on the events he is searching for. With the search terms he used there is no way he would get that result. You may argue that all the boring bits of websearching were cut, but for his second search he goes back to the web search instead of the newspaper's own search to get the next year's article. (00:22:00)
Revealing mistake: At the beginning of the scene where the Reverend sells the guns to Mel, Bobby is walking outside and it is rainy and stormy. But once he enters the motel room there is sunlight streaming through the windows. Then, in the next scene when he is outside with Rosie, it's stormy again. (00:34:00)
Revealing mistake: The marijuana plants being grown in the film are obviously not real. The plants in the film have very plastic looking leaves with no serrated edges like real marijuana.
Revealing mistake: In the scene near the beginning it shows a big guy converting a 7-10 split and celebrating. If you watch it closely you will realise that the 7 pin is lined up too far to the left and the ball is already in the gutter when it hits the pin. The movie makers could have at least bothered to repaint the pin placement lane markings so it would not be so obvious that the pin had been moved.
Revealing mistake: At the very end of the movie when Kyle Fisher is in the back yard in the wheel chair, he has stumps for legs. However, if you look at the bottom of the wheelchair just below the seat, you can see his feet behind him. It is especially obvious when the wheel chair tips over and his feet move a little.
Revealing mistake: After shooting in the door to Meg's office, the man in the darker jacket shoots the computer then steps into the room. John jumps him and grabs his gun (his shirt is unmarked in this shot). John then shoots him at point blank range. In the closeup of the shooting, the man's shirt is already torn - and the bloodpack/charge is visible through the hole - for a few frames before the gun is fired and the special effect goes off. (00:22:23)
Revealing mistake: One of the very last clips of the movie - one showing the barricade with a lot of flags - runs backwards. You can tell from the way the flags wave.
Revealing mistake: You can see the gun squib bulging out of the the police officer's right chest when he's shot. (01:31:05)