Factual error: At the climax of the movie, Alice swings the machete at Mrs. Voorhees and decapitates her. When the blade makes contact with Mrs. Voorhees' neck, her head flies off at an incorrect angle, as though the cut began on the opposite side.
Factual error: At the end of the movie there is the chase scene through the hedge maze in the dead of winter in Colorado. While Jack Nicholson runs after his son in a winter setting you cannot see their breath in what would be the cold night air.
Factual error: A solid gold cross of the size used in the film would weigh more than what any human could hold in front of them (nearly 200kg), much less as "easily" as the priest did at the end of the movie.