When Peter is escaping Westworld, he passes by a sign that says "Leaving Westworld," with several iterations in different languages. The French version says "Vour Quittez Westworld," but there's no "vour" in French - it should be "Vous."
On the next line, "doivant" is not a French word either. It should read "doivent".
In the last scene of the film, the gunslinger rises from the floor for the final time, and turns to reveal that its face-plate has fallen off. But the faceplate, clearly visible on the floor when the robot turns, wasn't there seconds before when the robot pushed itself up.
The opening commercial for Delos refers to traveling there by Hovercraft. However, the cabin shots of the transit vehicle show that the vehicle is capable of banking from relatively high up. Hovercrafts travel at a fixed low height above the ground and don't bank, therefore the transit craft must be an aircraft of some kind.
After the Chief Supervisor orders a power shutdown, accidentally locking himself and the other technical personnel in the control room, Peter finds them all dead of suffocation. The amount of real time that expired was less than an hour, and the technical personnel couldn't possibly have suffocated that quickly.
In the Western resort, the guns have a heat sensor which makes them impossible to be fired at a guest, who would be warm-blooded; the robots are not. Without body heat, the "interactions" with Miss Carrie's girls would be somewhat uncomfortable.
The guns in West world have heat sensors that prevent them from shooting guests due to their high body temperature, and can only be used on the robots. Assuming that the guests and the robots all have the same guns with this feature, how was the gunslinger able to shoot Blane? Furthermore why would they give weapons to robots that had the potential to harm the guests?
Right after John is shot, the Gunslinger says "Draw" to Peter. You can see the Gunslinger's breath (condense) just after saying it, despite the fact that he is an android. The Gunslinger model should not have any significant body heat, as that would have prevented a guest's gun from firing.