At the beginning, while Lucas is helping Will off his horse, and at the end when Lucas and Will shoot the gang, Lucasí first shirt button is undone. Thanks Ann Marie!
When Hank and the rest of the gang show up, Will exits the barn with the saddlebag on his right shoulder. When the camera changes angles, it has disappeared. (In the second picture, heís actually holding it in his right hand, below the camera shot. We see him raise it a few seconds later.) Thanks Ann Marie!