Revealing mistake: Ryan Reynolds is wearing red-eye contacts. You can see the whites of his eyes around the red circle of the contacts in several scenes - most noticeably, right after the home movie he's watching down in the basement melts.
Suggested correction: Not a mistake. Ryan Reynolds actually had bloodshot eyes from being awake for nearly two days of filming. He stated it in an interview for the movie.
Revealing mistake: When Shooter pins Mort against the tree with the shovel, you can see that it's a rubber shovel because it's bending around Mort's neck. [Mentioned on commentary]. (00:40:45)
Continuity mistake: When Vic and Josh are urinating on the slate, Vic holds it in front of him and the writing on it is perfectly legible, but when it shows him holding it out, it is runny and you can't read it.
Continuity mistake: After the fight on the barge between Michael and Marcus, Selene tries to revive the impaled and seemingly dead Michael. At one point she rips his shirt open to pour her own blood into his wound, then the shot changes to her face, then changes again, slightly further out. It is in this shot, you can see Michael's shirt is still intact.
Continuity mistake: After Jack shoots the dart at the crocodile trapped in the helicopter, it is visible in the animal's jaw. After the attack by the second crocodile, the dart has gone. A moment later it is back again. (01:09:20)
Visible crew/equipment: You can see a crewmember in the woods, when Jennifer throws the huge log at the guys, during the big chase scene. (00:05:20)
Visible crew/equipment: When Peck is falling down the stairs with the kid, you can see the back pad through his coat.
Continuity mistake: Clay puts a 'Have you seen Whitney' flyer on the back of the SUV. When the car drives past the Crystal Lake sign, it isn't there. When it parks, the flyer has returned and a guy removes it in anger. (00:24:35)
Continuity mistake: When Claire first sees the ghost, Norman rushes in and Claire grabs and hugs him. Her hand was just in the tub yet as she's hugging Norman, her hand is dry. She would have left some kind of a wet mark on Norman's shirt.
Continuity mistake: When Tina runs up the stairs and then falls through, she lands on a blanket but when she stands up, the blanket is gone.
Continuity mistake: In the scene where Benicio Del Toro is in the tavern listening to the townsfolk discuss his brother's death, you see him finish his alcoholic beverage, however, in the next shot his glass jumps to being half full.
Continuity mistake: In the scene after the bus rolls down (when they are at the beach), one of the girls is wearing a red bikini, but when she gets in the water it's black. (00:13:40)
Continuity mistake: The miner wounds Sarah's right forearm during the supermarket chase and the medic bandages it up. Yet, in all subsequent scenes, her arm is fine.
Continuity mistake: The blue van comes to the station and parks after the lights come back on in the diner. When the driver gets out of the van, the car has moved backwards a couple of meters. (01:06:55)
Continuity mistake: When Evy is trying to seduce Rick, and she finds him asleep in his chair, her hands move from his neck to the back of the chair between shots. (00:17:00)
Continuity mistake: When Shuya finds Utsumi dead, the proximity of her head to the girl behind her changes between shots, as does the position of her tie and gun beside her.
Visible crew/equipment: When Gary opens the trap next to the 2 school buses, he is wearing a cable attached to an earpiece on the right side of his head. The kind of cable actors wear to receive instructions from the crew. There's no reason plot-wise for him to be wearing it (he isn't receiving any instructions from the kids, who are right next to him).
Character mistake: When the 3 boys and Rogers are trying to recruit scouts, they pledge to Rogers and Carter raises his left hand but in the next shot he has his right hand raised. (00:09:05)
Continuity mistake: On top of the ladder, the Xmas lights wrapped around Shane change between shots repeatedly. (00:38:00)
Continuity mistake: When Renée Zellweger drives up in front of her house the first time in the movie, as she shuts her car off, her window is down. When she gets out, the window is back up.