I would like to draw your attention to a Pillsbury client alert which I recently scooped.
It was prepared by Sean F. Kane known for deep expertise in video game law, and it gives a decent overview on recent U.S. case law related to situations where the use of trademark protected material in video games without permission was confirmed as acceptable further to free speech right argumentation (First Amendment).
Illustrative citation from the introductory paragraph:
"We're telling a story and we have a point of view," EA's President of Lablels Frank Gibeau, said in an interview. "A book doesn't pay for saying the word 'Colt,' for example."
You may find this client alert here.