Continuity mistake: As Jesse, Diamondback and Homer try to black out the windows on their car (to protect themselves from the sunlight) Homer spray paints the window next to him black. The camera angle switches to a wide shot as the car drives by. At this time, the back window (which was just blacked out) has not been spray painted yet. It is totally clean again.
Visible crew/equipment: When Caleb punches the driver guy in the bar, the guy (who has now been replaced by a stuntman) goes flying backwards and lands on the pool table. When this happens, a wire can be seen on the stuntman, pulling him back and guiding his movement.
Visible crew/equipment: A cable is visible attached to the car during the explosion.
Revealing mistake: When Caleb is running for the van (during the motel shootout) there is a dramatic moment when he is shot in the back and is in pain. As he goes to wrap the blanket around himself you can see an orange tube leading underneath his clothing above his pants. Presumably this tube is pumping the smoke to simulate burning. (00:59:44)
Continuity mistake: When Severen kills the biker against the jukebox, the wall behind is clear of blood. A minute or so later, as Severen goes to kill the bartender, you can see the biker lying dead against the jukebox but now there is a large amount of blood sprayed on the wall. (00:47:21 - 00:48:45)
Plot hole: In the morning at the motel, the vampires have a big shoot-out with local law enforcement, which results in one at least one cop being killed. But when they escape, the police don't bother pursuing them or even giving them a another thought. Even for an 80's film, this is beyond ludicrous.