This fascinating article by Brian McMahon describes how the game of Monopoly was used during World War II to aid in the escape of Allied POWs.
(Is it just me, or does it seem from reading the story that this was an incredibly risky strategy — the Monopoly boxes contained maps that showed where Allied safe-houses were located within Nazi controlled areas. Wouldn’t it be a disaster if some of these maps were confiscated by the Nazis? Allied soldiers who were going off to fight were being told to look out for the specially-marked Monopoly boxes. All you needed was one traitor or P.O.W. to confess under torture, and the Nazis would know to intercept the Monopoly games.)