Continuity mistake: When Sharon Stone confronts Gene Hackman at the end, she throws the marshal star at his feet. It is an inch or two in front of his boots. After he is shot, he gets flung backwards several feet. Stone then picks the star up and throws it to Russell Crowe. She picks it up from behind Hackman's body, several feet away from where it landed but still sticking out of the sand the same way.
Other mistake: During the first round of the duels we see a part of the participants list and "Scars" is missing. He should appear between "Spotted Horse" and "Sparks" according to their order of entering the competition.
Continuity mistake: When Sharon Stone and the old man are talking in the graveyard it's raining. In the closeups, the sky is seen to be somewhat white and cloudy, but in the wide shots, the sky is a deep blue, and almost completely cloudless - and it's still raining. In the wide shot you can see the ground outside of the graveyard is bone dry.
Continuity mistake: Near the end, when Gene Hackman and Sharon Stone are finally duelling, the shadows change too fast. Before the first shots there are no shadows, then when Hackman has the little hole in his chest, there is a long one in front of him, and when Russell Crowe arrives, everything (even buildings) projects shadows over Hackman's dead body.
Continuity mistake: When Ellen flings the marshal badge towards Herod, it flies horizontally. You can even see it, still flying horizontally, on a downward curve as it starts to land. But when it hits the ground it hits vertically, so it can stick up out of the dust. It should be lying flat on the ground.
Deliberate mistake: In the scene where the characters are initially signing up for the contest, Gene Hackman's henchmen cock their weapons as they enter, then after Sharon Stone shoots the rope apart the henchmen cock their rifles again. The problem is that with a second cocking the rifles would be ejecting any chambered brass. It seems like a deliberate mistake because they cock their rifles an inordinate number of times throughout the movie; I would guess the director wanted the effect of hearing the weapons being cocked multiple times at the expense of continuity with the rifles.
Factual error: When Gene Hackman is shot at the end he looks down and sees the hole in his shadow. However if he was shot from someone at the same level as him, the hole would be straight, parallel to the Earth's surface. So if he could he the reasonably proportioned shadow the angle of the sun wouldn't show any hole in him at all.
Factual error: In the scene just before Harrod fights Ace Handlin, we see a view of Harrod's feet passing a blood stain in the dirt. This bright red color would be impossible when mixed with the dirt. Also we are led to believe that fights happen on the hour, each hour. The blood would have coagulated and been nothing but a dark spot on the ground. This has obviously been done to emphasize that the ground is bloody.
Continuity mistake: After almost every gunfight it rains, yet there's never any mud, or even wet spots on the ground afterwards - it goes back to being as dusty as it ever was.
Continuity mistake: Sharon Stone is warned at one point that the clock clicks before it chimes, the chime that tells the gunpersons to draw. The click is quite prominent in all of the times that it is used, but it only chimes after the click on a few occasions, and when it does, it's not the time indicated on the clock.
Continuity mistake: In the final gun fight, Stone is about to shoot Hackman a second time. Her arm is extended as she is about to fire. The scene shows Hackman and then goes back to Stone. Her arm is now bent as if she is drawing to shoot.
Other mistake: Final showdown between Ellen and Herod. The first shot hits him in the torso. He does not move and seems surprised to find a hole there. Second shot to the head, from the same gun, lifts him off his feet and drives him back several feet, a very different reaction. Quite possibly at some point it was supposed to be Cort that shoots him first, from behind Ellen. Ellen would be wounded but then fire the killing shot.