During the scene in which Albert tells Vincent about meeting his brother, Albert says, "Vincent, Vincent, I swear man, tonight's the best I can do for you." His mouth clearly does not match what he says.
When Chris first fires his weapon at the white pickup at the drive-in the sound is that of one shot being fired, yet the instant the impact is shown on the pickups windshield there are two bullet holes.
In the opening sequence when Neil walks to the ambulance, he crosses a street and then must step onto a small grass median between the curb and the sidewalk. In doing so the Foley footsteps don't change from footsteps on a hard surface to those on dirt or grass.
When the police are staking out Waingro's hotel room they use a camera on their hotel room door's peephole. After the fire alarm goes off, the door is opened and the display of the camera on the television in the room doesn't move in accordance to the movement of the door.
The shootout begins near the plaza at the intersection of Flower and 5th streets. After Bosko is shot Hanna gives chase and the getaway car is seen speeding, passing the spot where the shootout begun. Once McCauley starts shooting through a windshield window, the same spot is seen being passed again. The car is then seen passing the intersection, but once the tires get blown the car is at the intersection again with the plaza just few steps away.
When Hanna goes to his hotel after leaving Justine, he walks to the balcony to look out at the city lights. The camera angle changes to a view from behind his head so you can see the view, but the hair color and hair style of the man seen from behind is noticeably different - obviously a double.
During the armored car heist the guys lay down a spike strip to blow out the tires of the police cars. The first police car hits the strip and drags it underneath. In a later scene the spike strip is visibly undisturbed.
When McCauley shoots Van Zant, he fires the pistol empty, as the slide is clearly seen in the locked back position. In the very next shot of the same scene, the slide is forward and the gun appears ready to be fired.
When Vincent returns home before seeing his wife putting on makeup, Vincent looks at the dirty dishes in the sink, where we see a dirty plate in the left sink, and a wok with dirty dishes in it in the right sink. After Vincent comes back downstairs ("Okay, where are YOU goin'?), there are no dishes in the left sink and the dishes that were inside the wok in the right sink are gone.
In the bank robbery/shootout scene, a Lincoln Town Car is used as a getaway car. While the exterior of the car has been dressed up for the movie to appear as a brand new 1995 model with newer headlights, header panel, grille, taillights and wheels, the interior is still that of a 1990-1994 Town Car.
Near the end, when Neil and Eady are driving the interstates of L.A., at one point they are approaching an interstate ramp curve to the left. In the next shot, they are clearly in a curve to the right.
After the delivery man in the white truck is shot at the drive in, he is clearly seen inside the vehicle slumping down and dying from his injuries. In the next scene right before the truck glances off the concrete wall, the driver is sitting up again.
When Vincent first gets out of the car at the bank robbery and shouts "Police! Move!" we see a couple coming towards him jump out of his way. In the next scene with Vincent, we see the same couple walking past him again.
While investigating the armored car scene, Detective Casals is wearing an eyelet collar shirt (indicated by the collar pin under his tie). Later in the same night when Vincent calls asking if Albert Torena called, Casals is wearing a dress shirt without eyelet holes.
At the beginning when Neil and Chris are in the ambulance waiting; Chris puts on his white hockey mask before Neil but when the camera shoots from outside the ambulance when it moves off only Neil's white mask can be seen.
When McCauley, enters the bank front entrance its clearly seen its a street level a few seconds later camera is at floor level while watching him walk across the lobby a window is seen at left of picture that clearly looks like the bank lobby is several floors above street level, how did he get up 5 or 7 floors in just a couple of seconds?
When McCauley confronts Charlene in the hotel room, a coat hanger is visible in the mirror behind Charlene. When looking directly at the rack (which is located behind McCauley), the coat hanger is not visible.
In the final scene, the approach light system at LAX airport is shown turning on and off for individual aircraft as they approach to land. In actuality, approach lights to runways remain lit at the same level of intensity for aircraft. They are not turned 'up' and 'down' for each airplane.
A Parsons graduate working in a bookstore makes no logical sense. When they first meet, Eady tells Neil that she's a graphic designer, and that she went to Parsons for it. She also says working at the bookstore is "a day job, until I get enough going." Anyone with a degree in graphic design from the prestigious Parsons School in New York City, especially in the mid-1990s, could get a well-paying job in graphic arts anywhere they wanted, even before they graduated.
After the bank robbery, Michael tries to escape, and in so doing, trips and falls into a pond. When he gets up to take the little girl hostage, he looks dry. The suit is indeed wet though, which is evident when looking closely. It just doesn't seems that way. Some fabrics look similar wet and dry.
They make off with $12 million divided into 3 duffel bags. Assuming they are divided equally there would be about $4 million per duffel. $1 million in $100 bills weighs 20 lbs so each person was running and shooting and jumping over cars carrying over 80 pounds.
During the bank robbery getaway, McCauley fires through the windshield at the police in front of them. He is using a fully automatic weapon yet only a couple of bullet holes appear while he is firing. While it is possible several rounds went through the same hole, the scene is still completely inconsistent with an actual event.
When Vincent in Air 18 contacts JJ in Air 40 wanting to know the whereabouts of Neil, JJ says Neil is "on the 105 heading east towards the 110 interchange." After Vincent gets into the car on the Vermont on-ramp, they pass-through signs above the freeway clearly indicate they are traveling west on Highway 105, not east.
Neil's crew is stealing over twelve million dollars from the bank divided up into three very large seabags that are worn over the shoulder. With that much money, each bag would weigh over eighty pounds each, yet when they are escaping from the bank, they are running with the bags of money as if they weighed almost nothing.
While Hanna is interviewing witnesses to the armored car heist, there is an abandoned TV playing outside. The TV is showing a blue "input" signal, despite being an older model that would be incapable of doing so; it should only be capable of playing static.
At the beginning of the sequence where Hanna drives up to a light, stops his car, and throws out his TV set, two extras on the left sidewalk can be seen waiting for the 'action' cue before they start walking.
When Vincent visits Albert at the wrecking yard, Vincent enters through the doorway and takes a right, then turns left, then left again, and then right through the door to where Albert was sitting. Vincent could have just walked straight through to where Albert was, but it looks as though Vincent took the long way around - the path along which the camera traveled - to appear more dramatic.
The goof item below may give away important plot points.
In the final scene, Hanna becomes aware of McCauley's position by a shadow near his feet. In the following aerial shot, it is obvious that McCauley's position could not cast a shadow to where Hanna is standing. McCauley's shadow would have been cast mostly onto the structure he was hiding behind.