Continuity mistake: When Jesse and Frank are telling the doctor that his son was killed (right in the beginning of the movie) Jesse gained a lot of beard growth in five minutes. When they are outside talking to Zee, he has just a light beard, and then when they go inside he has a heavier one.
Other mistake: There's a horse that has apparently ridden up a cliff, and an electrical burning brand that can be changed onto different flame settings.
Continuity mistake: When Francis Fryer throws the cowboy he loses the scarf in his hand but when the camera angle changes he has it again.
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.
Factual error: When the posse arrives at the mission, a horizontal jet stream can be seen during this scene. (01:00:00)
Continuity mistake: After Evans was shot near the end of the movie, Ben Wade jumped out of the train to look at him. If you look over Wade's shoulder, you will see that Nez (the Apache) had already arrived at his spot, and Campos (the Mexican sharpshooter) threw Wade's gun belt to Charlie Prince. After the movie cut a couple of times, Nez was shown walking up, throwing Wade's gun belt to Campos, who then threw it to Charlie Prince.
Factual error: When Clint Eastwood first goes to the barber shop, the barber very deliberately sharpens his razor the wrong way, flipping the blade with its sharp edge against the strop - this would instantly dull the blade. No real barber would make this mistake, but it's a common movie error.
Factual error: We learn that the previous sheriff, Charlie Wade, took revenge on anyone who smuggled illegal immigrants across the border in the late 1950s - we are shown the smuggling, as Eladio Cruz hides a group of Mexican men in a watermelon truck to take them across the border. However, in the 1950s, the border was not fortified the way it is now - the smuggling shown would simply not have been necessary.
Continuity mistake: During the desert chase sequence, when our hero is run off the road by Ernest B. his missing arm is momentarily transposed when he steps from the jeep.