Revealing mistake: When David goes to the house and picks up a bat to protect himself while walking through the house he is attacked from the back, and you can see his protective knee pads when he kicks against the wall, before he is suffocated.
Revealing mistake: Visible blood pack on the waitress's back when she gets stabbed by Otis.
Revealing mistake: When the guys are on the jet skis, when they are showing off, you can tell they are stunt doubles.
Revealing mistake: After the car chase, the authorities are seen carrying away two body bags that are clearly empty. The men show no strain at all in carrying the bodies, and the bags even look empty. But if they were, they'd just be folded up and taken by one person.
Revealing mistake: In the first person shooter sequence, when Reaper gets the chainsaw, there are many parts where he is moving it around near Pinky, now the beast thing, and it does not have a shadow, and at other times when it is at the same angle, it does.
Revealing mistake: In the beginning of the movie, at the scene in the morgue, dead David's eyelids very slightly shake right before his casket is closed. (00:04:20)
Revealing mistake: During the fight in the apartment, the girl in the shower is wearing a black thong. (01:44:00)