Stay after the credits. There's an additional scene where John goes to visit Chas' grave and leaves a lighter, then as he's walking away you see Chas with wings and he flies up into the sky.

Jay and Silent Bob (from Kevin Smith's films) get a mention during the movie. When talking about sidekicks, three are mentioned, the first two by name, and the third is a description of Jay and Silent Bob.

The name of the Mexican guy who found the Spear of Destiny is Manuel. (It's revealed in the opening scene, when his fellow calls after him in Spanish.) Manuel is the Spanish form if Immanuel, the name of the Messiah according to the Book of Isaiah. Occult interpretations of the Bible commonly claim that Immanuel will be the name of Antichrist.