Other mistake: Although the film is set in Oklahoma (and north of Oklahoma City), the roads are marked by Texas road signs.
Other mistake: If the bullets from the super gun move at just under the speed of light, how come the bad guys can't hit him or the girl? The bullets would arrive almost instantaneously and that would mean minimal compensation for them running. Plus the guy had them locked on when he shot.
Other mistake: After Guy gets hurt in the warriors/ducks game, the scoreboard is shown. It says that there is 15 seconds left in the third period, when it is really the second period.
Other mistake: Speaking to General Hershberg (Michael Moriarty) in his office, Nat Serling (Denzel Washington) implies that it was easily discoverable that the US tank was destroyed by "friendly fire" because the US is the only country which uses "uranium depleted" shells. The correct term is "depleted uranium". Maybe Washington flubbed his lines.
Other mistake: Carolyn Stilton shoots Blondie O'Hara in the head and is lying dead over her dead husband. Just before the final scene starts she begins to open her eye.
Other mistake: Jack's parents were at a Halloween party when his mother went into labor. Later in the movie when he's asked by his teacher he says his birthday is September 12th.
Suggested correction: The movie doesn't specifically say this is a Halloween party. This may simply be a costume party which can and do happen multiple times a year.
As you stated, it doesn't say it's a Halloween party. In fact, there's signs in the room that say "Beaux-Arts Ball."
Other mistake: When the students are below deck having a meal, a glass pitcher of orange juice can be seen. Even though the boat is apparently rocking to and fro in the waves, the juice level stays still. Obviously it is the camera that is moving and not the set.
Other mistake: Look closely at the dead trooper's closed eyes. You'll notice during the length of the shot that his closed eyes move. Fast forward to make this more obvious. (00:37:55)
Other mistake: Vanessa is illiterate, but easily reads the Hi-Way Café menu. (00:48:35)
Other mistake: Early in the movie when Shale is screening the commercial for his "services," the rolling text describing his abilities lists "Helicopter Repelling" instead of "Helicopter Rapelling".
Other mistake: When the killer and Segal are fighting in the last scene, and the killer is thrown out the window, you can clearly see the black shards on the window bend.
Other mistake: In the scene where Nicole opens her locker and a note from David falls out, the handwriting is exactly the same as the seen where Nicole leaves a note taped to the bedroom door for her father. Although the letters are larger, the same applies to the note on the father's vandalized car, which says he's popped both of their cherries.
Other mistake: When Roy is about to hit the ball off the porta-potty, the TV commentator bets Romeo that he won't hit the shot onto the green. Roy's shot ends up on the fringe of the green, not on the putting surface itself (an important difference), but Dewey collects the bet.
Other mistake: When Kitty reads Michael's letter from England to Harry, there's some strange smoke arising from behind their chairs. (01:19:40)
Other mistake: During a chase, Gibson makes a left turn at an intersection causing two girls to suddenly lunge backwards to avoid getting hit. The girl with the long black hair turns to her friend and smiles. This was most likely because she just successfully played a part in a big movie, but I don't think she'd be smiling at that moment. Most of the people in that shot don't react normally but are more explainable given the New York setting.
Other mistake: After John T's passing, the screen caption reads "1 year later" and they are celebrating his birthday. The light flash happened on his birthday and took three months to be diagnosed and die. The caption should actually say 9 months later.
Other mistake: Shooting two forty-fives at once is hard. Willis must think so too. One gun fires blanks and the other gun operates like a real pistol, even emptying out shells, but is not firing. This is very noticable in slow motion during his first standoff.
Other mistake: In the scene where Bess' body is thrown into the sea there's a shot of Jan's head injury. The area around the well healed scars is freshly shaven and shiny. Such a long time after the last surgery there would be at least some stubble. (01:25:15)
Other mistake: The subtitles keep changing the defendant's name between Buffano and Boffano.
Other mistake: Towards the beginning of the movie Dorothy first "meets" Jerry by eavesdropping on his conversation with a woman in the airplane. But Jerry is located in first class whereas Dorothy is in coach. Going by her seat location it seems like she's sitting at least 10 rows from Jerry, plus the area that divides coach from first class between them. And Jerry is speaking in a soft voice. Add to that the drone that an airplane makes (even if not airborne) and it's highly unlikely that she would have been able to hear him, even if he was the only person talking in the plane (also unlikely).