In the hockey arena scene Paul Walker is hit above the eye with the hockey puck and blood starts coming out, yet in the next scene the blood is coming from the mouth, with no apparent damage to his eye.
When Oleg shoots Anzor and the bullet flies through the window Joey's just asked Nick to throw him a piece of bread. Later on, in the slow motion replay, he's just got up from eating from his plate instead.
In the scene where Theresa finds Oleg with the bag over his head and gives him CPR, there are no "surgical implements" on the closet floor. When she inspects the closet in the next shot, she finds all of the equipment.
During the opening shootout, the Jamaican with the machete lunges at Rydell and swings his machete towards him. In the next slow-motion shotgun shot, the man's arm is still behind him (showing that he hasn't swung yet).
In the hockey rink when Oleg is pointing the gun at the man about to kill Joey with the shotgun, the camera shot from the front has him holding the gun with one hand and the rear camera shot has him holding the gun with two hands.
When Dez talks to the girl in the "play room" scene, a close-up of her is shown on the TV screen. Then the camera operator starts moving backwards and the camera that feeds the TV screen zooms out too quickly so that the film camera (presumably a Steadicam system) has not yet left the viewing angle of the TV camera and can clearly be seen on the left side of the TV for a moment.
Oleg has asthma attacks throughout the film and needs his inhaler to relieve them. In the pharmacy scene, he says he needs Beclovent. Beclovent is a corticosteroid inhaler used regularly to prevent asthma attacks, it has no effect on an attack that is taking place. Beclovent would not provide any relief for Oleg as shown.
When the hooker takes Oleg into the drug store for a new inhaler, he asks for Beclovent. The Pharmacist even says, "Yeah, I know." Beclovent is an inhaled cortecosteroid, not a rescue inhaler. It is of no use during an acute asthma attack (which the pharmacist would know) and is no longer being manufactured in an inhaler form.
When Joey returns home after being shot in the diner, Teresa opens the door to his Mustang and pulls him out. The body of the Mustang is that of a 1967 model, but when the door is open the interior door panels are from a 1968 model.
In the opening scene, the first Jamaican drug dealer is killed during a slow motion shotgun blast. In the shot, the shell is being ejected immediately as the shotgun is fired, which should not be the case as the hijackers were carrying pump action shotguns whereby the shell is ejected upon pumping, not firing.
Blood, like most body fluids, appears fluorescent under black lights. In the arena scene, none of the blood is fluorescent. However, blood does not show up under black light until it a chemical called Luminol is added.
The goof item below may give away important plot points.
When Tommy is threatening to kill Joey, he holds his Beretta pistol to Joey's neck. He cocks the pistol and waves it around; when he puts it back to Joey's neck, the hammer is down again. Further, after he shoots Sal, the hammer is again down - but the gun should still be cocked.