Revealing mistake: At the beginning, when the grandma zombie knocks off that guys head, a geyser of blood pours out. When the body falls forward and the blood splatters the camera, the body lifts up about three centimetres before it falls down, indicating that it is a dummy.
Continuity mistake: When the first zombie attack at Marion's house occurs, he throws his guns in the air, takes off hypocrite copper's shotgun and shoots a zombie. He then drops the shotgun and grabs his handguns. From the aerial shot the shotgun has disappeared. THEN the copper picks it up off the floor a few minutes later.
Factual error: In the convenience store scene, "Chip" Chipperson walks in and cops a shovel in the top of the head. Then he starts walking forward and a sign stops him, and the shovel pulls out, tearing off his face. Shouldn't have it torn off the front of his head?