I came across an article today about another use for an innocent game that everyone is familiar with, in some shape or form. It seems that during World War II, British intelligence in conjunction with the British makers of Monopoly created special editions of the popular board game to include maps printed on silk, money, compasses, and other tools to aid prisoners of war in escaping from German war camps. The article gives much more detail...and if I were still homeschooling would spark a whole weeks' worth of study of World War II!!
You can read the article at Get Out of Jail Free: Monopoly's Hidden Maps