Cindy is wearing straplike sandals that secure around the ankle during the fight scene between her and Brenda in Mr. Meeker's science class. When the fight breaks out, both girls are on the ground for no more than 30 seconds, and when Cindy gets up without her top and runs to the door, she is seen without shoes, and that particular style could not likely have fallen off or be easily removed during the fight.
During the rape scene in the locker room, Heather is conscious and alert until after the rape is over, when Jake kicks her in the head and leaves her bloodied and unconscious. Later, when Vince flees the Scars, he has a flashback to the scene, which shows Heather being raped while bloodied and presumably unconscious.
Red is wearing a black leather jacket when he and Fargo confront Brenda in the warehouse. After Brenda kills Fargo and Red finds his body, he is still wearing the jacket as he falls upon the bear traps that cause the injuries leading to his death. However, when Jake sees the two strung-up bodies in the warehouse, Red's jacket is gone and he has a bear trap clamping his right forearm. Had Brenda removed Red's jacket afterwards, she would have had to remove the bear trap to do it.
When Brenda confronts Fargo in the warehouse, he is wearing a headband. When the arrow is seen going through Fargo's throat, the headband is gone.
Just before Brenda confronts Red and Fargo outside the warehouse, Red hands his cigarette to Fargo. But as Brenda speaks to them, the cigarette is back in Red's hand.
When Jake follows Vince to the alley in his car to run him over, the person that Jake is aiming for and ultimately hits is obviously a stuntman. We do see Vince once he's bleeding on the pavement.
When Brenda sets Jake on fire after pouring the solvent on him, the close-ups of Jake on fire reveal a hooded figure, obviously a stunt double.
After the fight scene between Cindy and Brenda in Mr. Meeker's science class, she gets up without her top and runs to the door. At this point you can hear faintly in background the director yelling "cut cut" and the scene continues quietly for a couple of seconds. Showing the editor did cut the scene early enough.
While the girls are working out in the gym, the mic and boom supporting it just hover over Brenda's head.