Reason crime reporter C.J. Ciaramella filed a FOIA request for any FBI files on TSR Hobbies, the creators of Dungeons & Dragons. The incident is largely forgotten now, but the FBI actually raided the TSR offices in 1980 because its agents thought that a scenario in the Top Secret RPG was actually a real assassination plot.
Along with records related to that 1980 raid, the FBI sent him what was essentially Gary Gygax’s FBI file (PDF).
As Ciaramella summarizes the file in Reason,
An FBI source in the report alleges that Gygax was “eccentric and frightening,” carried a weapon, proudly responded to every letter he received from an inmate, and had a Liberian holding company. It concludes: “He is known to be a member of the Libertarian Party.”
. . .
In short, Gary Gygax wasn’t a snitch and fought the power.