During the torture scene Nik's last lip ring disappears and then reappears before he is killed.
After Bobby rolls snake eyes (both 1s) with the dice, the dice are shown in a side view and you can see one of them is a 5.
When the kids' car breaks down, they take off shirts and jackets to walk in the heat. Moments later, in Rusty Nail's barn, you can see their breath when they talk.
When Melissa is driving away in Rusty's big rig, it is pouring rain. When her boyfriend escapes from the trailer, he falls onto the ground and dust flies up.
When Rusty kills Nick with the pipe bar, the prop bar on Nick's head is already visible under the chin while the pipe bar is going through his head.
At the end of the movie, when the truck goes over the cliff on fire, you can see inside the engine compartment and there is clearly no engine.
[23:10 to 24:22]One of the girls asks, "why is Bobby taking so long?". He had only been gone one minute 12 seconds.