Continuity mistake: At the beginning, Hull watches as Eastwood beats up the guys in town. When Hull gets up on the wagon, his hands are fine, but in the next scene he has a bandage, I believe, on his left hand. Then the bandage is gone again and reappears soon after.
Continuity mistake: When the preacher stops La Hood's son Josh from raping Megan, he shoots Josh's revolver from his hand, then shoots his hand, then shoots the revolver away from Josh with two more bullets. In the next shot where Josh rolls away, the revolver is back in its original position.
Continuity mistake: Eastwood puts five or six bullets into the lead bad-guy at the climax of the big shoot out. As the bad-guy Marshall pitches forward, you can clearly see the bulging outline of the blood pack beneath his clothing.
Continuity mistake: Near the end of the movie, Eastwood is tossing sticks of dynamite into the "bad" miners' camp. He tosses one stick into a tent. After it blows up, you can still see the stick of dynamite on the ground at the entrance to the tent, with the fuse still burning.
Continuity mistake: When Preacher is about to kill Stockburn, as he walks toward Stockburn he reloads his revolver by replacing the cylinder. He briefly points the pistol at the camera, you should be able to see bullets in the chambers of the cylinder but they are empty. Again, just before Preacher actually shoots Stockburn, he points the revolver at the camera and you see empty chambers where you should see the unfired bullets. (01:47:40 - 01:48:20)