Visible crew/equipment: In the shootemup scene at the hangar, at the beginning of the film, Castor Troy shoots an agent in the stomach and the agent flies back - you can see the wire pulling him backwards.
Continuity mistake: At the end of the film, when Nicolas Cage and John Travolta are lying next to each other in the ambulance, there is no blood on Travolta's shirt collar and suddenly, between shots, the collar is covered in blood.
Visible crew/equipment: When Sean first visits the Walsh Institute, he, Dr. Miller and Dr. Walsh walk in front of the circular glass window to view the ear reconstruction. In the next shot facing them, the reflection of a boom operator holding the boom pole is visible on the glass in front of Dr. Miller and Sean.
Visible crew/equipment: At the L.A. Convention Center, just before Castor Troy (as Sean Archer) disarms the bomb, there are a few shots of all the extras evacuating the area. In the interior shot, that looks out through the glass doors onto the street, the tracking crane arm with a seated camera operator and camera on its platform is visible as it shoots an exterior crane shot of all the extras, which was seen among the previous shots.
Continuity mistake: When Archer and Dubov are making their escape, Dubov falls over the rail and Archer catches his gun barrel then tries to save him. In the last shot before Dubov falls, Archer is holding on to the very last tip of the gun, but in the wide shot he is holding a lot more of the barrel.
Continuity mistake: When Castor (as Sean Archer) is speared, as he stands there singing morosely his shirt is drenched in blood, but when he is next seen in the ambulance that blood on his shirt has vanished. Additionally, the cuts on his face produce blood trails which smear, when he is first speared, but in the ambulance his face is cleaned up and the blood trails are thin and neat.
Revealing mistake: At the boat scene when Archer is holding on to the red boat and is skiing on the side, you can clearly see the waterproof boots he is wearing.
Revealing mistake: In the big speedboat scene near the end, when Cage is hanging off the side of the boat the stunt double is obvious in wide shots, where the entire boat is visible from above. He has big long sideburns, which are in stark contrast to Cage's short hair, visible in closer shots. At various other points in the movie, stunt doubles appear of much different physical builds than the two actors, with markedly different hair colours, and I seem to recall that at least one of them had facial hair.
Visible crew/equipment: On the runway, two shots after Castor Troy says, "This is a big gun. Fly the f*ing plane," there is a side shot of the Hummer. As the camera pans in closer, the reflection of a crew member on the filming vehicle, which moves beside the Hummer, becomes visible at the Hummer's back end, just before it cuts away.
Revealing mistake: When Loomis comes upon Castor grieving over Pollux's body and says "Sir, why are you so upset? Its just Pollux Troy", you can see discoloration of a lump on his forehead which is makeup covering the blood pack where Castor will shoot him.
Visible crew/equipment: When the red boat has hit the barrier and Castor Troy and Archer fly through the air, you can see a wire attached to the front of the boat just for a split second, then when it falls in the water and explodes.
Factual error: In the hangar scene when Castor and Archer point their guns at each other, if Castor's gun was really empty the slide would be locked back.