Continuity mistake: When Bugs is performing his shooting stunt in the saloon, you can see the entrance behind Sam has nothing between it. When Sam tells Bugs he's missed, we cut to Bugs who says "Wait!" and then return to Sam, and this time there are doors between the entrance.
Continuity mistake: When Bugs shoots Sam in the face when trying to shoot a can, the can lands in front of Sam. In the next shot, the can has disappeared.