Deliberate mistake: In the parking lot at the horse track, the old cars are so huge, they don't fit properly in the tiny modern spaces. They are hanging over the backs of the spaces so badly that the drivers would only have about two feet to try and get their enormous cars out of the spaces.
Deliberate mistake: When Harrison Ford and Mary Lynn Rajskub are crossing the tracks, its Rajskub who's driving the car, not Ford. This is because the filmmakers originally had Rajskub driving the entire way. They later refilmed the drive with Ford driving, but kept the shot of them crossing the tracks the same. Ford and director Richard Loncraine confirm this on the special features of the DVD.
Deliberate mistake: In Saw III we learn that Amanda was the person who abducted Adam from his apartment. However, if you watch his abduction in the first Saw film, you'll see that the person attacking him has the hands of a middle aged man.
Deliberate mistake: In all the shoot-outs, the bullets that hit the cars spark, which bullets do not do, and leave no hole, dent, or even a small scratch. They do, however, break the glass.
Suggested correction: This isn't correct. In the big shootout towards the end, gunshots leave holes in car doors and break car windows from both sides of the fight.
Deliberate mistake: When Jenny writes "dick" on Matt's forehead, she does not stop the beam but the word is written with the letters separated.