Corrected entry: The narrator along the course of the movie is Denzel Washington, and we're led to believe his character is the one telling the story. But as we've seen throughout the movie, Azazel takes the voice of anyone he possesses. Of course it would be silly to have a cat narrating the film, but Azazel is not in the same body as the narrating voice at the end.
Corrected entry: When Denzel shoots John Goodman in the end, he uses a semi auto. But he bends down to pick up the gun and it's a revolver. A few seconds later, it's a semi auto again. (01:49:00 - 01:51:00)
Correction: He has the semi auto still in his hand as he picks up the revolver.
Corrected entry: There is a scene in which Denzel Washington is required to shoot a person on a city street who is possessed by a demon. Washingon uses a Glock pistol and fires only one shot. In the scene it is clear after the shot is fired that the gun's slide is in the locked back position (this only happens after the last round is fired. A Glock typically holds between 8-15 rounds). In the next frame, while Denzel is still holding the gun in the shooting position, we see that the slide has been moved forward. (01:17:00)
Corrected entry: Hobbes types "February 11, 1966" into the search engine and is taken to the front page of the "Chronicle" newspaper. The date on the page is a bit hard to read, but it definitely says 'Wednesday'. In 1966, Feb 11 was a Friday. (00:22:40)
Correction: As a supernatural being, I imagine he can use any voice he wants, in addition to any body.