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.
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 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.
When speaking with Neil, Kelso says about the bank job, "..to give you an idea of where my estimates come from...". In the next scene, after Nate is done talking with Van Zant, Kelso then contradicts himself and tells Neil, "...these are not estimates, these are exact figures."
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
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 the young hooker is in the motel room with Waingro, her hair is loose and shoulder length. Shortly thereafter, after she has been killed, Vincent pulls back the sheet covering her face, and her hair is in dreadlocks.
Moments before the street shootout starts, Michael Cheritto is the first to exit the bank. He walks calmly up to the waiting getaway car with Donald Breedan waiting inside and opens the front passenger door to get in. In the next shot he climbs into the back of the car.
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.
When Eady first meets Neil in the café, she leans over and reads aloud from the cover of the book he is reading, "Stress Fractures in Titanium". The book with either this as a title or subtitle does not exist.
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.
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.
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.
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.
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.
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.
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.