Factual error: Near the end of the film Knox is flying a Huey helicopter and the Angels hitch a ride by shooting it with a spear gun and dangling on the line behind it. Suddenly adding about 200kgs to a Huey in flight like that is going to cause all sorts of problems with the trim and airspeed of the aircraft - the pilot would know immediately that something was wrong. (01:23:20)
Continuity mistake: The tyres on the crotch rocket motorcycles they were riding kept changing from knobbly tyres to road slicks, back and forth depending on what terrain they were on. Easiest to see when Ethan skids on the road to avoid the white van - clear shot of slick tyres - then about 30 seconds later they're on the dirt, he skids into the old car and you can easily see that he's got off-road tyres front and back.
Revealing mistake: There are supposed to be two dead young Asian males sitting in the back of the car, but in this shot, it is so obvious that there are two dead 'dummies' riding in the back. Also, in the crash, a few seconds later, very blatant dummy heads are flying everywhere. (00:40:40)
Plot hole: There must be a lot of dumb scientists in Sebastian's lab. While defibrillating the invisible gorilla, (s)he becomes completely visible for a moment. However, not once do the scientists consider that applying a mild electrical shock to the system renders the invisible animal visible again - that electricity may be the key to the whole invisibility problem. They don't even comment upon the fact that the gorilla does become visible.
Plot hole: Peter goes into Carl's mind to save Catherine. When he's in there he sees the tank with the water nymph. On the tank are strange symbols which provide the FBI with the clue needed to find the latest victim. Makes sense so far. But, go back to the scene just after the FBI have captured the comatose killer and are looking in his basement. The FBI are looking at the contraption that the killer uses to suspend himself over the victim. On the contraption is the same symbol seen later on the water nymph's tank. Why didn't the FBI follow up the symbol then?
Factual error: Gary Sinise looks at a computer screen with a short section (about two full twists) of DNA on it and proclaims that "This DNA looks human." He could have been looking at DNA from any single-celled organism and it would have looked just as human as what he was looking at. All mammals have 90+ percent of their DNA in common, he would have to have sequenced the entire DNA strand (something like 3 billion pairs of nucleotides) to identify it as human, something that would be totally beyond the capacity of anything but a well-equipped genetics lab, something they show no sign of having.
Continuity mistake: When Wolverine crashes into the tree knocked over by Sabertooth, notice that the entire front of the truck gets completely folded up and the windshield breaks into a thousand pieces. In the next frame, Wolverine gets thrown through the unbroken windshield and the front of the truck is practically undamaged... (00:18:05)
Continuity mistake: In the third segment of the movie we see Davis, Yolei, Cody and their Digimon playing on the beach. In the wide shot when we see all of them playing we see that Davi's Digimon is in his "rookie" form, Veemon. When they show a closeup of him and Davis together, Veemon is now in his "in training" form DemiVeemon. Then they show them all playing again and he is now Veemon again.
Continuity mistake: When Cage's character offers the money for his brother and the brother is in the car about to get crushed, the back window gets broken out twice. (00:15:55)
Visible crew/equipment: In the scene after Patrick Bateman's second encounter with the detective in his office, we see Bateman having sex at Courtney's apartment. After he rolls off her, Bateman approaches the large, stand-up mirror in the bedroom. In the upper right hand corner of the mirror, a boom microphone can clearly be seen moving around to pick up Christian Bale's lines. The next time we get the same long shot, the microphone is gone. (00:52:45)
Other mistake: When Sugimura is looking for Kotohiki, he activates his scanner to see if she is nearby. The scanner shows her location, but fails to show either Mitsuko or Kiriyama, who show up quickly after.
Character mistake: At the memorial service the principal says that it's been 39 days since 39 loved ones had died. But there were 40 students on the plane and 4 chaperones, making the total 44. Now 7 people got off the plane, which means 37 people related to that memorial service actually died, not 39. Two pilots would make up the numbers, but there would be flight crew too, which still leaves the numbers off.
Visible crew/equipment: In all the President Kennedy White House shots, you can see the boom mic peak down several times. Look for the group shots, and the boom mic will be there.