Continuity mistake: Harry's dog, Meathead, changes genders. It's a male dog while jogging in the park, but is female when the mob hit man is sniffed out at the hotel. Then it goes back to being male.
Visible crew/equipment: At one point Clint Eastwood is out in the woods practising his shooting with his new .44 auto-mag pistol. While he's doing this, a car pulls up and a black male begins to get out with a shotgun. (We later learn that this is his partner). As the man with the shotgun is opening his door, if you look at the reflection in the car window, you can clearly see the reflection of a man with a camera and another man standing next to him.
Continuity mistake: On Harry's way to and from the fish market, it changes from day to night too fast.
Other mistake: When Harry gets to his vacation spot he is greeted by a dog. A few seconds later the dog is seen lifting his leg to pee, showing his dog is a male. Later on in the film after he returns home after the main killer has killed the second victim, the dog is scratching at the door. If you pause the movie at this moment you notice the dog has a sagging belly with nipples just like a female dog after delivering puppies. (00:48:05 - 00:57:20)killer_sobe
Factual error: In the final gun battle at the end of the film, Harry shoots the last bad guy so he falls off a high spot on the roller coaster and through the roof, into the carousel building. Yet as the credits roll, there is an aerial shot and you can see the carousel building at the left of the screen, with no hole in the roof. Also, the carousel building and the roller coaster are about 200 yards apart.