When Cliff is killed in the maze, the killer slices his stomach with his right hand going from right to left. In a later scene, Hank explains he is looking for the left handed killer. He states the cut on Cliff was "left to right".
Juan's shirt is covered in blood before he breaks the hot tub window. Once the water runs over everyone, his shirt is clean. Later, his shirt is covered in blood again.
When Juan, Penelope, Jenny and Lars are running from the killer in the jungle toward the end of the movie, when they go into the jungle it is night. The next shot shows The Sun just starting to rise above the forest trees. In the shot that follows, the three are running in the jungle in broad daylight.
Towards the end of the movie, when they come out of the club house just after Juan breaks the hot tub, the watermelon is behind the pretzel, then in the next shot the pretzel is behind the watermelon, then in the next shot the watermelon is behind the pretzel again.
When Lars startles Jenny from behind she lets a mouthful of her red drink spill out, but when she turns around there are no stains on her clothes and her face is perfectly clean.
After Coconut Pete's body is found, one of the brief close-ups of his face shows this supposedly dead man's lips moving.
When Carlos bends over to pick up the trash bag, his shadow doesn't follow his movements.
When the killer throws the machete through Putman's chest, no blood ever comes out.
When Dave is showing the activities board, Hank's name is not on the board at all.