Revealing mistake: Doug has the hologram when inside the alien nuclear reactor, and a bunch of bad guys encircle the holographic image and fire at it at point blank with automatic weapons, and not one bad guy gets hit. If they encircled the 3D image, at least a few bad guys would have been hit by their own men. (01:37:00)
Revealing mistake: When Arnie uses the dead body as a human shield, watch the corpse's mouth - he grimaces every time he gets hit (the squibs hurt). (00:31:00)
Revealing mistake: Pay attention to the drywall on Quaid's left just as he exits the bathroom to a rain of gunfire. If you look closely there are discolorations in the paint where explosive charges are packed and set to detonate in lockstep with the shots - creating "bullet holes". (00:25:00)
Revealing mistake: In the scene where Sharon Stone attacks Arnie in their house with a knife you can see that the knife is a fake because it bends. (00:26:00)
Revealing mistake: When Quaid throws the bullet-ridden body down the escalator, you can see Richter and Helm have both been replaced by stuntmen. Their hairstyles are totally different. You can also see that the 'dead' man is still alive as he's flying through the air (slow motion helps). (00:29:55)
Revealing mistake: When Arnold jumps through the glass, you can definitely see a change in his face and body shape. (From the stuntman). (00:30:05)
Revealing mistake: When Lori punches Doug in the crotch, you can see that Arnold Schwarzenegger is wearing some kind of padding under his pants to soften the blow. (00:25:35)
Revealing mistake: When Doug and Melina are being chased by the drilling machine, it punches through a wall. When the machine comes out again it pulls some rocks with it, a very large one hits Melina and she doesn't even flinch, obviously because it's a fake rock. The size of rock should have knocked her to the floor or potentially killed her.
Revealing mistake: Right before Quade jumps on the train to get away from Richter, he uses a gun to break one of the train windows. His gun barely (if at all) touches the window and it shatters. (00:31:40)
Revealing mistake: When Arnie blows the old lady disguise mask on Mars Immigration, they shot him and the dome crashes. Right after the soldier gets sucked out of the room, some extra comes rolling and kicks the camera. (00:47:05)
Revealing mistake: In the scene in the Mars Air/Spaceport, the troops are wearing Casio scientific calculators on their wrists. (00:43:50 - 00:46:55)
Revealing mistake: When Quade shoots Dr. Edgemar, Lori yells "Now you've DONE IT.", and the wall explodes, which is plainly made of foam. Many of the pieces of 'wall' tumble lightly across the floor. (01:05:40)
Revealing mistake: When Richter's arms get cut off and he falls down the elevator shaft to his death, you can very obviously see the outlines of his real arms inside his shirt when his leather jacket flies up as he falls.
Revealing mistake: During the scene when Quaid is escaping from Harry and his men, he slams two guys into the concrete wall behind him. The "concrete" wall shakes when the two men hit it. (00:22:25)
Revealing mistake: In the last scene, when Douglas Quaid and Melina are holding each other and looking over the landscape of Mars while the sky gets colored, the camera starts from top behind them (looking down) then moves down while looking at them, so more and more of the Mars horizon gets visible. But the camera-tilt goes too far up, so at the top of the picture, you can see the blue-screen curtain and the pole and rings holding it. Douglas Quaid and Melina are just looking at a blue-screen. (This is visible on the video; on the DVD an extra black top-bar is covering it.) (01:48:55)
Revealing mistake: Sharon Stone gets shot dead, but she moves afterwards.
Revealing mistake: After the fight with Richtor, Arnie throws his severed arms off the elevator. If you look closely at the bottom of the elevator you can see the arms do not fall all the way down. They disappear once they hit the floor of the stage Arnie is acting on - they forgot to animate some arms falling on the bluescreen image.
Suggested correction: Rictor's arms were torn off when the elevator passed through a floor or a tier or something. Is it not possible that this is where the arms fell to? I don't think they were meant to fall all the way down...
You missed the point of the mistake. It's not about the arms falling to the Mars ground. As the elevator platform is moving up, we can see the background below the platform. When the arms are tossed over, they should be visible below the platform as they fall, since it's open space. But in the scene, the arms just disappear once they hit the real life stage ground because they weren't added in during post.