Revealing mistake: After Hank shoots Lou's wife in the kitchen, the camera shows Jacob walking into the house, then Lou's body on the floor with a puddle of blood around his head. If you watch closely, you can see Lou's left eye twitch.
Revealing mistake: As Bobby drives along the dirt roads at the start of the film, in one shot when the camera is filming inside the car, you can clearly see the gear is in park position yet the car is "driving." (00:01:55)
Revealing mistake: The money that the two gang members are counting in the opening view of the hotel room scene is obviously fake. Notice how white the bills are, when they should be greener and have more of the random anti-counterfeit features. (00:02:00)
Revealing mistake: When Phil drives the truck off the cliff, you can see right through the grill of the truck (meaning there is no radiator or engine), and the transmission is also missing, as you can see when the truck is falling upside down. Without an engine or transmission it would be hard to drive off a cliff.
Revealing mistake: At the end of the film Vanessa gets crazy because Bob kills her grandma, and she starts beating him up in the caravan, hitting him and throwing various stuff at him. Throughout the scene, Reese Witherspoon's' stunt double is really obvious. Her hair looks completely different!!!
Revealing mistake: When the windshield is shot up, Riggs knocks the glass off the car. But interior shots that follow show Riggs' tall, fluffy hair isn't moving at all in the high-speed air rushing into the car. (00:02:15)
Revealing mistake: When Marcus (dressed up as Tiffany) is braiding Karen's hair, you can easily tell that the corn-rows were already done, and that the hair that is not done is a wig. You can see the line where the wig starts. Also, it's probably a wig because when Marcus (as Tiffany) is braiding the hair, he just looks like he is moving it, and that the braids are already done. (00:49:25)
Revealing mistake: When Conrad throws the Russian over the cliff, as the Russian explodes, you can see that poor CGI actually makes him transparent.
Revealing mistake: Al Pacino talks to the older man named Ron in a club filled with mirrors. If you look at Al Pacino's lips when "Ron" is speaking you can see Al coaching the actor playing Ron on his lines.
Revealing mistake: In the scene with the motorcycle riding on its rear tire, skid marks can be seen from previous takes.
Revealing mistake: Near the end the psycho killer pays a black man to beat him up so that he can then blame the injuries on Dirty Harry. Watch the killer's hairdo as he gets punched and beaten: a couple of rear-view scenes show an obviously fake wig, intended to look like the killer's own bad-hair-day style. (01:16:05)
Revealing mistake: At the start of digging the tunnel, one of the characters (I think Denny) calls Woody Allen, "Woody" by accident.
Revealing mistake: When Clint Eastwood and detective Jay Winston are talking in her office she walks over to the blinds and touches the plastic piece that closes them but nothing happens, they stay the way they were. She does this twice. (00:25:46)
Revealing mistake: When Gene's bodyguard (the one with the moustache) shoots Slasher and Duke, just before Slasher is shot the bullet hole effect is visible on her forehead (sightly concealed by make-up) just before the actual 'shot'.
Revealing mistake: When Bronson is chased up onto the rooftop by one of the gang members, Bronson pushes the guys over the edge of the building, and it is visible that it is a dummy taking the fall.
Revealing mistake: Watch Andy Garcia's decapitation scene. His head starts to come off before the sword makes contact with his neck. Slow motion helps but is not required.
Revealing mistake: When Draven sends T-bird to his death in his car, the real Ford Thunderbird is replaced by a fake mockup using a flimsy one-piece fiberglass body mounted on a pair of straight axles. When it explodes, the body lifts off in one piece, warping wildly while the front axle simply falls away. No proper car components like engine, transmission, suspension and so on, are seen anywhere, though they should be. (00:57:05)
Revealing mistake: When Hightower throws the football to the hood, the hood flies back to hit the door. After he hits it, you can see the black wire that pulled him.
Revealing mistake: During the night surfing scene notice that the sun is evident in the background (look closely it does not appear long). There are also shots where you can see clouds and faint blue sky. Moments later you see Keanu and Lori sitting in the water with completely different lighting which was actually taken at night and further distinguishes that the surfing shots were not actually done at night time. I heard the scene was shot during the day with a filter so it looked like it was shot at night.
Revealing mistake: When the bleached dead girl is lying on the table, you can see her breathing. (00:13:45)