In the birthday party scene, MacKenzie clearly blows fire into the clown's face. Yet in the next shot the only part of his clothing that is burning are the legs of his pants; his upper body is fully intact.
When Mackenzie has been kidnapped and tied to a chair near the end, the candles on her cake go from lit to unlit and back as the camera zooms out and back in.
The glass that the clown punches through changes between shots: when we first see it, it has wire mesh in it, but when he punches through it, it does not.
In the scene where Mackenzie's father is at the grill BBQing, you see a remote control in his shirt pocket. The remote control disappears and reappears in several shots.
During the hot tub scene at the party, a bottle of alcohol appears by the cans of beer in one shot, and then disappears completely in the next shot.
The town's name of "Blanca Carne" ostensibly means "white meat" in Spanish, but the grammar is incorrect. In Spanish, adjectives follow nouns. The name should therefore be "Carne Blanca".
When Val shows off her "new" tattoo, you can see the body hair on it. Any true tattoo artist would have shaved the entire area before tattooing her.
When the clown is pouring gasoline on the girl, the blonde girl blinks when she is supposed to be dead.
Side window glass on a Cadillac Escalade is tempered glass and would break up into small pieces, not stay together in large shards.
During the party scene, the drummer's movements do not match the music heard.
Camera crew reflected on the side of the truck when the police are dusting for fingerprints.
The entire crew is reflected in the detectives' sunglasses when they go to question Mr. Benjamin.
Mackenzie's camera is stolen and when it's returned to her, after she develops the film, there are photos of the first and second murder. But the camera was not stolen from her until *after* the first murder had taken place.