Visible crew/equipment: In the taxi scene, you can see that the taxi is abnormally high, and there's a special strut rig under the front part of the car so it doesn't take a destructive beating in that whole racing scene.
Continuity mistake: When McClane (Willis) approaches the dump truck in the aqua duct, the driver pulls an Uzi submachine gun onto his lap. The camera then cuts to McClane being seen in the door mirror of the truck, then cuts again to the cab being shot full of holes by McClane. The gun on the driver's lap changes to an MP5K (in this case, a Daisy MP5K Airsoft Replica).
Continuity mistake: The sun is coming up behind McClane at the end. Particularly noticeable in the shot where McClane is shooting at Simon. The previous and following shots show a black sky.
Continuity mistake: The damage to the sedan during the shootout on the road changes. The windshield goes from being normal to full of cracks.
Revealing mistake: Towards the end of the film when Simon and his men are found by McClane (Willis) and Zeus (Jackson), Simon's men can be seen taking MP5K submachine guns. The guns are actually Daisy MP5K Airsoft replicas. At one point, a man "pumps" the forward grip of the gun to cock it. Indicating it as an airsoft gun and not a real submachine gun.
Continuity mistake: When the cab drives between the two trucks it comes out without a scratch. When it crosses the park it is damaged all over.
Continuity mistake: After exiting the aqueduct, McClane falls in a puddle, hair slick, soaking wet and covered in mud. Zeus calls him and McClane turns around. In a brief shot from behind him his hair swaps to clean and fluffy.
Visible crew/equipment: At the very beginning of the film a bus passes the camera. A reflection of a crew member is visible. Its fast but clear enough to see that he has his arms crossed.
Continuity mistake: In the taxi, when Zeus is telling John his name and asks if he has a problem with that, John's hand is not against his head. In the next shot it is.
Continuity mistake: Near the end, after the huge gold heist, Simon Peter Gruber and his psychotic lover, Katya, engage in rough celebratory sex, ripping off each other's clothing, such that Katya's upper torso and black lace brassiere are fully exposed. A few minutes later, when John McClain interrupts their sex, Katya's shirt is fully closed.
Visible crew/equipment: After the school evacuation scene starts the four kids trapped in the school look out the window to see what the commotion is. The next shot through the window grill shows a camera crew filming the evacuation from the street as they come up behind the cops on the upper right. Footage from the camera crew on the ground is proof of this. The footage is from the exact same time, about 30 seconds earlier in the movie. You see an African American boy and woman running off to the left of the screen through the police who are trying to guide everyone straight out from the stairs past the fence. The boy continues running but the woman is grabbed on her left arm by a cop who turns her back around to go through the fence. The boy is wearing a yellowish orange shirt and tan shorts and the woman in a brown outfit, a blouse with white buttons and pants. (01:40:10)
Character mistake: Why didn't Joe, Connie, and the students just run back down to the front entrance of the school? They had plenty of time instead of making the effort of going to the roof.
Suggested correction: No, they couldn't. They barely made it to the roof on time and that was closer than the front entrance.
Continuity mistake: The cab drives in between two trucks and drives further up. When McClane says "I didn't say Park Drive" watch the rear window and the truck he passed by 50 meters away is now really close behind.
Continuity mistake: Before the cab drives through Central Park McClane slams on the brakes. Skid marks from previous takes can be seen on the pavement.
Revealing mistake: When McClane is hanging on the steel cable which pulls their car to the river, right when he says "Run, run" there's a brief shot and it's very obvious that the guy is Bruce Willis's stunt double.
Revealing mistake: After McClane chases the ambulance in the cab, he is driving the wrong way down a one way street. Notice the tyre marks on the pavement from previous takes. The cab follows them to a T.
Character mistake: When McClane and Zeus are in the cab travelling east on 72nd street, as they approach the park Zeus says "we need to go south!" he points to his right, which is north. When McClane crosses 5th Ave., he turns his steering wheel to the right, thus heading north.
Revealing mistake: When the bomb explodes at Bonwit Tellers at the start, we see a van fly into the air. You can see the devices that throw it upwards.