Corrected entry: Throughout the movie Emmett wears his holster on the left, but in the opening sequence, when Emmett dives to the floor, his holster is on the right. Also, he was supposedly startled out of his sleep, and we see him grab his gun out of a holster he is not wearing, but when he dives to the floor to shoot the guy on the roof, suddenly he is wearing his holster.
Corrected entry: The night before the jailbreak at Turley, when Emmet and Paden are standing in the street discussing the plan to break Jake out of jail, on the roof of the building behind them is about 4 inches of snow. The next morning during the jail break we see at least 2 inches of snow on the ground, yet as the posse is chasing our heroes out of town suddenly the snow is gone and the ground is dry.
Corrected entry: When Mckendricks men order Mal and Ezra Johnson off Ezra's Homestead Mal Asks one of the cowboys "Do you know what a Henry rifle can do in the hands of someone who knows how to use it?" Ezra is unarmed with his right side facing the camera. In the time it takes the cowboy to answer "Who would that be, You?" Ezra (who is sitting double on Mal's horse) produces a Henry rifle and throws down on the cowboys it wasn't in his right hand in the preceding scene and if it was in his left he'd have to pull it over Mal's head and switch it to a right hand grip to be in position to cover the cowboys (presumably while they sit there and let him do it) there wasn't time between shots.
Corrected entry: In the scene when the bad guys are going to burn down Kate's house, they throw a kerosene lantern to start the fire. Pause the film right before they throw the lantern and then advance frame-by-frame. You can see the fire start from behind the bookcase a couple frames before the lantern hits the bookcase.
Corrected entry: After the Glover fight scene when Cleese tells him to leave, Glover walks back to the bar to drink the whisky. Listen for the distinct sound of swallowing/gulping before Glover puts the shot glass to his mouth. After his drinks, there is no sound at all.
Corrected entry: In the scene where the sheriff (John Cleese) is playing chess in the jail, if you look carefully you will see that it's a reproduction of the famous Isle of Lewis chess set that is sold by the British Museum. One would wonder - especially since the original hadn't been found yet - how it got to the Old West.