When Ellen shoots Herod in the chest, the hole that goes clear through him allows light to be visible through him, yet when Herod lands on his face the back of his jacket has no such hole.
While Cort and Herod supposedly have their gunfight at dawn, the sun is significantly higher in the sky, revealing it's much later.
When The Kid draws against Scars, the closeup shot appears to show him shooting left handed, but the film is actually reversed, indicated by his revolver's ejector rod being on the wrong side of the gun's barrel. After Scars fires, the distant shot of The Kid shows him holding his revolver in his right hand.
(at around 22 mins) Eugene Dred is offering the bar girl a piece of jewelry in a "business discussion." On closer inspection it's a ring on a chain, the same ring he is seen taking off the late Ace Hanlon's left pinky and stringing on a chain less than four minute later at 46:02.
There area no shards of wooden chair under the Marshal's scaffold or anywhere nearby as John Herod and his men ride away.
A bullet fired from a gun held by an adult cannot carry enough energy to pick up an adult and throw him back several feet. To do that, the shooter would also be thrown back several feet, by Newton's third law of motion; or the gun would be too heavy to carry.
The entire idea the movie is based on, with two opposing gun fighters meeting face to face in the middle of main street to quick draw, is actually extremely rare to find actual examples of in the American Wild West. With the exception of the famous "Wild Bill" Hickok - Davis Tutt shootout on July 21st 1865, finding documented occurrences of this is extremely difficult. In reality you would try to shoot your adversary in the back, or it would be some other ambush scenario.
Watching the Swede load his cap and ball percussion revolver, I noticed that he put the powder, then the ball and then a patch and tamped it down. It's powder, patch then ball and tamp.
At the bar, Mexican music (mixture of trumpets and strings) are heard. But this genre of music -Ranchera or Mariachi- was not popular or commercially exploited outside of western Mexico until about 1920. Still the trumpets were not added until 1950.
In the final gunfight, Ellen's bullet is shown going towards Herod's eye. This would tend to knock him backwards from the top. A brief shot, confirms this, showing Herod's legs pivoting backwards from the top. But the next shot shows Herod flipping heels over head and landing face down. This would only be possible if he had been hit near his feet, and from behind.
About 25 minutes into the film Sharon Stone's character is at the bar drinking and "Kelly" challenges her to a shoot out. There is a Standing Liberty Quarter visible on the bar, presumably in payment for the drink. The film takes place in the 1870's, but that type of quarter was not made until 1916. (Correction) The decade the movie takes place in is not given. It may or may not be the 1870s.
After Cort shoots Spotted Horse his priest collar is removed by Herod. While during the shooting Cort it seems like he is not wearing a collar at all, he is. The collar dirty and stained with sweat, and in blends with the color of the skin in the VHS release. However, this can be spotted in the remastered version.
Herod challenges Cantrel to a fight. When this happens, there is a heavy rainstorm occurring. However, when they fight, the ground is dry. Several times in the movie, scenes with rainfall are followed by scenes (according to the story happening right after the storm) where the ground is completely dry. There were no gun fights on this day due to the rain. The fight between Herod and Cantrel takes place the following day.
The ground dries very quickly, however the town of Redemption is located in a dry heat/desert area where the constant sunlight causes rainwater to evaporate and the ground to dry up more quickly.
The hangman's noose or knot, has 5-7 coils, not 11 or 12. The reason being is that the more coils you have the more friction, which would prevent the noose from closing properly, which increases the odds that the person being hanged can wriggle out of it. It is also a knot which wasn't used until the early 1900's, twenty to thirty years after this movie is supposed to have taken place. (Correction) The early 1900s is not necessarily 20 to 30 years after the movie takes place. It is not given when the movie takes place. Given the technology, fashion, and culture, it could be as late as the early 1900s.
When Ellen in supposed to be on horseback at the beginning of the movie, she is standing still looking upon the town. When the gang of horsemen run by her, the camera's frame is too big because you can see she is pretending to hold on to reins. In actuality, she is not sitting on a horse and she is holding up nothing.
When Scars is dragged away during the sudden downpour, his legs and feet drag the wet dirt. But neither he nor the bearers leave any marks in the mud, revealing it to be cemented soil to make film production easier.
Before the final duel between Herod and Ellen, as Cort uses a rifle to shoot one of Herod's bodyguards over his shoulder, you can see the rifle is not remotely pointing at the man, yet he falls dead anyway.
After shooting Herod in the head, Ellen is directly facing the camera and you can clearly see that the cylinders in her Colt SAA are empty.
When Herod fires the first shot at Ace Hanlon, the gun is obviously pointed at the ground when the flame bursts out of the gun.
When Herod duels Sargent Cantrell, the bullet goes through Cantrell's head leaving a huge hole that is front to back, the diameter of 4 inches. Such a large wound would be impossible with such a small caliber weapon, but even if it was a larger caliber, the entry wound would be smaller than the exit wound from such a weapon of this period.
At 32 minutes 24 seconds there's a shot of Sharon Stone from the chest up. If you look closely there's appears to be a small line of white light that lays vertically right over her face. Perhaps something missed in the editing room.
The Armani logo on Ellen's sunglasses.
During the gunfight between Ellen and Cort, there is a close up shot of Ellen's eyes including her contact lenses.
Ellen and Herod drink champagne from "flute" glasses, a particular design that was not created until the 1930's.
When the bartender is filling the peanut bowls it is obvious the big peanut jars he is feeding from are made of plastic.
Remington-Peters did not begin stamping "R-P" on their ammunition until the 1960s.
When Herod shoots the gun at the chair Cort is standing on, the sound of the gun is heard before he pulls the trigger and before he is finished aiming the gun at the chair.
When Herod shoots the gun at the chair Cort is standing on, there is a sound of a ricochet before the round hits the chair.
(at around 1h 35 mins) When Herod gets up just after the explosions, the camera pans up. In the background on the right side is a shadowy figure (perhaps a pyrotechnician) wearing a thick flak-vest and holding a radio control.
Instructions are given for the fights to commence at the first chime of the hour on the clock. So much attention is given to the click before the strike, that the clock is never actually heard chiming.
During the sign-up for the contest, Ace tells the barkeep "Put an ace up there, everyone will know what it means." The barkeep actually draws a spade, which is one of four units in a standard deck, that could represent any card from ace to King.
In the second round fight between Cort and Spotted Horse, people are standing dangerously behind each of them, directly in the firing line.