When Billy hits Suzanne Lempke in the car, she hits the windscreen and leaves no blood on it, but in the next shot there is blood all over it.
The position of the Gypsy after she is hit by the car.
Towards the end of the film, Billy's right hand is still bandaged and bleeding before a knife is stuck into the wound to open it again, yet later on his hand is not only without any dressing, but with no visible scar at what is apparently only a few days later.
After Gina shoots Billy in the hand, he holds it up. to where you can see through it. Part of the bone should be visible. If the bone is gone, why does his middle finger still work?
When Linda is talking to her father in the kitchen towards the end of the film you can hear her saying "I'll catch you later" before dipping her finger in the pie, but her mouth doesn't move.
Though Billy loses a great deal of weight through the course of the film, his wedding ring always stays the right size for his finger.
When Bill is talking with Hopley in his study about the gypsy curse, if you look carefully at a picture frame on the left on a table, you can see a microphone boom moving in the reflection of the glass.
It seems unusual that Quigley the real estate agent would settle for a mere $800 from Billy not to tell Heidi and Dr. Mike his whereabouts, when the missing persons flier Quigley shows Billy advertises a $5000 reward for information leading to his return, especially given the fact that Quigley seems to be a somewhat unsavory individual.