Continuity mistake: When Bugs is having a laugh contest with Witch Hazel, you can see the wall behind him has a hole in it. But in a close-up of Bugs, the window has gone.
Continuity mistake: Daffy takes down a gun from the mantle, but when Daffy points it at Bugs in the next shot, you can still see the gun on the mantle.
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.