During the driving scene at the beginning, when the camera shot is on the driver's side pointing toward the ocean, the vehicle seems to be traveling at a slow speed. However, when the camera shot is on the passenger's side pointing toward the houses, the vehicle is going noticeably faster.
On their way through the kitchen when Jenna, Dougie, and their mother are going to confront Satan in the basement, the mother grabs a knife so that the blade is facing her. In the next shot it is facing away from her. One shot later, the blade is once again facing her, but she is turning the blade away from her.
The goof item below may give away important plot points.
In the confrontation with Alex, Satan shoots through
his left hand, and in the subsequent scene in which he is dressed like Jesus, he has an obvious wound on his left hand. In the scene in which Jesus attacks Alex, however, the wound is gone.