The last time Doc fires the shotgun from the taxi, it switches from his right to left to right hand.

When Doc and Carol exit the hotel, neither is carrying a bag. Doc then drops the bag when he flees. When they encounter the old man with his truck, they have the bag back again.

When Rudy puts the pistol in the hotel manager's mouth, he cocks the hammer, but in the next shot, the hammer isn't cocked.

Shaving cream on Doc's face after the shave.

Gollie should've have called the police when Rudy first threatened him with his life.

EDIT - He didn't call the police because he runs a sideline in forged passports and other forms of identification. He would lose all business if he ratted out a fellow criminal.

When the police cars are chasing Doc and Carol after they have robbed the gun store, one of the police car tips over, and the log, used by stuntman to turn cars over, can be seen rolling down the road.

In the opening sequence, Doc and Carol are practicing their shooting. One fires a Colt .45, and the slide stays to the rear, showing that it is empty. However, the crimped end of a blank round can be seen to be stuck in the ejection opening.

The shadow of a crew member can be seen moving in the mirror of Rudy's motorcycle after he shoots the beer can.