Continuity mistake: Before John Smith shoots the man above the skylight in the hotel, he reloads his two pistols. When he shoots the man, he only fires the gun in his right hand. In the next shot, we see two empty magazines fall to the ground as he reloads again.
Other mistake: Shooting two forty-fives at once is hard. Willis must think so too. One gun fires blanks and the other gun operates like a real pistol, even emptying out shells, but is not firing. This is very noticable in slow motion during his first standoff.
Visible crew/equipment: Towards the end of the motorcycle/armored car chase the armored car forces a gray sedan off the road into a concrete barrier. Just as the sedan begins to corkscrew into the air you can see a camera just ahead on the middle of the highway. Then we see the perspective from that camera as the car flies towards it. From yet another camera just behind the flying sedan we can see the sedan actually land on and obliterate the camera. In the next shot you can see the armored car run over the remains of the camera which then go skidding down the highway.
Factual error: The phones in town are crank type or candlestick type that require an operator,as mentioned by the hotel owner at the beginning of the film.John Smith calls Georgio at the telephone office by dialing the number,impossible on a system with no central office switching equipment.He would have just used the patch cords and pressed a button to ring the phone.
Other mistake: Upon entering the bar to rescue the bartender, Willis shoots his first victim clean through a window. In slow motion you can see the gun is never fired and yellow flash is edited in.