Continuity mistake: In the final scene at the sheriff's office, Mitchum has his feet up on the table top, and the boot soles are clean. But after Wayne walks out, there is suddenly a spot on a boot sole. (This is visible in the video)
Deliberate mistake: When Raza is chasing the "empty" train, as it goes over the trestle just before he stops it, you can see the engineer in the train's engine.
Revealing mistake: As Jango fires the machine gun, the ammunition chain hanging from it is loaded on both sides, and it doesn't move. Also the belt has different sizes of cartridges in it. (00:45:30)
Revealing mistake: In the last scene, when Chris is leaving, it shows several shots of the peaceful village. Each time they show the village, in the middle of the square is what looks like two boys fighting. One punches the other and he falls down and gets up and punches back and he falls down. They do that about three times.