Visible crew/equipment: When Neil (De Niro) breaks into Van Zant's apartment and shoots him, watch as Van Zandt flies backward. You can see a wire running up through the bottom of his sweat pants.
Other mistake: In the scene where Pacino is talking with Albert outside, when Pacino starts singing, the soundtrack on Albert's dialogue is way off.
Visible crew/equipment: In the drive-in shootout scene, the camera and crew are visible in the rear view mirror in the cab of the white Dodge pickup fleeing De Niro and Kilmer.
Revealing mistake: In the scene when Pacino leaves the police station to go to his hotel for a shower, the camera is pointing up a tree lined street. Watch the pedestrians - they are all standing still until the car comes into view then someone obviously shouts action and they all start walking.
Continuity mistake: In the scene where Neil is coming out of the elevator at the hotel Waingrow is staying at, you seem him switching his flashlight to his right hand while he reaches up with his left hand to set off the fire alarm. In the next shot, we see a close-up of his RIGHT hand setting off the fire alarm. The shot after this, you seem him lowering his LEFT hand from setting off that alarm, with the flashlight still being held in his right hand.
Visible crew/equipment: When Neil is sneaking up at Van Zant's house, you can see both Neil's and the camera man's reflection in the glass windows on the house.
Visible crew/equipment: When Vincent Hanna decides Neil is already gone, he heads to his hotel room. He enters the room and walks out onto the balcony. The shot of him approaching the balcony and opening the sliding door is shown from outside, on the balcony itself, and the cameraman (wearing a white shirt) and camera are visible reflected on the left side of the sliding glass door. It is more evident as the shot progresses, because the cameraman shifts position and the reflection moves further to the left, becoming larger. (02:21:54)
Continuity mistake: When the agents are doing surveillance on the hotel room, they have a camera connected to the "peep hole" on the adjacent door. There is a TV monitor that the agents are watching. When the agents open the door to leave the room, the door with the camera on it opens, but the picture on the monitor stays the same.
Revealing mistake: When Neil & Co. are in the restaurant after the armoured car robbery, they all get up to leave to deal with Waingrow. The next shot is from the parking lot of them leaving the restaurant. Right as the shots switch, they are all standing still lined up at the door for a second, and then they start to move out the door (once the director yelled "Action" I'm sure).
Continuity mistake: When Vincent is sitting at the table drinking whiskey and talking to Justine, the remote control, the bottle, the glass, the bottle cap, and the chicken leg all keep changing positions. Yes, he does pick up some of these items, but right after he drops the chicken leg to the table, the camera switches to Justine. 2 seconds later, it goes back on Vincent and all those items have moved at once.
Continuity mistake: Robert De Niro finds Val Kilmer in the apartment and they are discussing Kilmer packing it in. Kilmer is all stressed out, and decides to light a cigarette - using a Zippo lighter. The sequence of events is: Val Kilmer grabs a cig, smoke rises from the cigarette, THEN you hear the click of the Zippo lighter.
Continuity mistake: In the scene where Al Pacino is confronting Hank Azaria about his relationship with Ashley Judd, the position of the knot in his tie changes during the scene. (I saw this error noted under "corrections", but if you watch closely, the knot is almost completely under the left collar tab of his shirt between shots.)
Other mistake: After the post-bank robbery shootout, a TV reporter is heard describing the shootout as taking place in a "small southland neighborhood." But earlier one of the detectives was heard ordering road blocks at Flower and Figueroa, meaning the gun battle occurred in Downtown Los Angeles. Hardly a small neighborhood.
Visible crew/equipment: In the scene where Hanna and Casals break into Hugh Benny's apartment, when they break down the door it can be seen that a stuntman is filling in for Pacino.
Continuity mistake: When Neil sets off the fire alarm in Waingro's hotel, there is a little red sign above the fire alarm when shown from far away. When it shows his hand up close pulling the alarm, the red sign is gone.
Continuity mistake: In the shootout scene when they drive away in the car, De Niro is seen in slow motion as he realises there are cops in front of them as well as behind. He raises his weapon and fires, knocking the rear-view mirror off the window. In the shot directly after he is seen still firing his weapon and the mirror falls off the window again.