Revealing mistake: When Cliff Booth is driving Rick's Cadillac, in some angles the speedometer is showing 0 (zero) as the car is driven down the boulevard.
Revealing mistake: When Julie is talking to Stuart about her future, snow is falling in front of her. We can also see the wind is blowing, as it moves her hair. The snow, obviously CGI, is still falling straight down, and doesn't interact when the wind blows.
Revealing mistake: The film was rushed to theaters, leaving a few mistakes which Universal fixed. In the original cut, toward the end, Judi Dench's human hand is visible, complete with her wedding ring. This was fixed for the re-release.
Revealing mistake: When Nix tells Miles, "Just kill Riktor for me," Nix rushes out shooting at everyone, and in some of the following shots the actress has chroma key fabric wrapped around the two "missing" fingers which Dane severed earlier. The chroma key fabric was used for effects editing, but those shots were missed in post production. After Nix has opened her trench coat, those fingers are "missing" properly. (01:21:10)
Revealing mistake: At the start when they're clearing the White House field Little Rock shoots her gun without her finger on the trigger. (00:04:20)
Revealing mistake: When they're playing kickball the first time (when Phil sucks at it), the shots change from either the sun rising/setting to fog and cloud cover.
Revealing mistake: The detectives start interviewing Linda and tell her they will be recording it. The detective pulls out a phone, and we see it recording. He starts talking and the waveform is moving but doesn't match when he speaks. If it were accurate we would see a peak when he talks.
Revealing mistake: The use of a green screen (or other color) during most of the cafeteria scene is obvious if you watch the people in the background instead of the main characters and is flawed in a few ways (e.g, varying angles, greater distance, continuity of a person, etc). For example there is a man wearing a blue shirt/tan pants and carrying a briefcase walking down the aisle toward the Good Boys' table. When the man is walking along the wall that is behind the Good Boys, he is further ahead than he is when he is picked up again. Also, this man shows up in front of Max when Max is walking to Soren's table. The man also appears walking along the back wall with a woman. Watching the wall behind Thor and Lucas, it is sometimes at an angle and other times looks more distant. Some of the people would essentially be walking "out of the wall" in order to appear where they do (e.g, the boy with a backpack).
Revealing mistake: When Phil approaches Michael's grave, water ("rain") has already accumulated only in front of the grave. When Phil is kneeling by the grave, streams of "rain" fall behind him and in front of him, but not directly on him. (00:25:03)
Revealing mistake: The headlights on Hayley's car are fake (i.e, blocks of white to represent headbeams). (00:30:36)
Revealing mistake: After most of the people trying to hang onto other people holding onto the ascending helicopter fell off, a downward view from the helicopter showed a man effortlessly hanging onto the landing skid and a woman just as effortlessly grasping his jacket's shoulder. (00:02:50)
Revealing mistake: When the zombie crawls into the hardware store breaking through the bottom part of the barricade, you can already see on the wood plank the line where the wood is supposed to snap in half. (01:05:20)
Revealing mistake: The camera holds on a close-up of the article featuring the 'Female President of the Network' Caroline Morton for 3-4 seconds, long enough to allow to quickly browse the text and easily see that it's a generic article about women in workplaces used as filler text and not the interview Katherine is reading. (00:03:25)
Revealing mistake: Ron leans against a barrel and sets in motion a series of events leading to an explosion. For being able to tip it with such a modest push, it is obvious it was empty (confirmed also by how it bounces). (00:02:20)
Revealing mistake: In the semi-POV shot showing Elena's face as the SUV rams into their getaway car, the passenger window is open - which would make no sense in the heated car chase with bullets flying all over the place, and is not consistent with the rest of the scene either. Just helps filming. (00:24:35)
Revealing mistake: During the interview, you can see a monitor with the lyrics of "Something", even though he is supposedly improvising.
Suggested correction: This is a deleted scene. It is in the extras on the DVD but it is not part of the movie.