Continuity mistake: When the Monk tells Kar that he's going to help him with his fighting skills, you see the other 2 Monks standing behind them, one in front of the other and one of them puts his hand on the shoulder of the other. The camera angle changes and you now see them standing side by side.
Revealing mistake: At the end when the Monk With No Name has turned old and is walking away from Kar and Jade while waving to them (without looking back), you can see a finger on the left side of the screen covering up the corner and side of the lens. This is for sure in the wide-screen DVD version.
Continuity mistake: When Kar goes back to the warehouse to find the Monk, he pushes the door open and the 2 women hold up swords to his chest. The camera angle changes and the sword on the right is now on his shoulder. The camera angle changes again and the sword is back against his chest. You also see him standing with the doors almost closed against him when they were fully opened in the previous camera angle.
Continuity mistake: When Kar wakes up Jade who is sleeping on the couch, she grabs his neck with her feet and pulls him over the couch where you see her feet pull away from his neck. The camera angle changes and her feet are again wrapped around his neck as he's pulled over the couch.
Continuity mistake: When the Monk does his flip to avoid getting hit by the car, the bad guys get hit and their guns go flying in the air. You see the guns spinning in the air and they are facing the opposite direction from each other. The camera angle changes and you see the Monk grabbing the guns and they are now facing the same direction before he grabs them.