It isn't exactly a wargame, but Coin Age is a neat little game that you can PnP for free and play with some spare change. The kickstarter is a pay what you want, but it has a pledge level wherein you can order a copy of the game and also donate copies to Operation Gratitude, which mails care packages to U.S. soldiers.
My brother and my dad both served during wartime, my brother in Gulf 2 and my dad during Vietnam and Gulf 1, and I know how much my brother appreciated it when he received little things from the states. Black licorice and playing cards were particular favorites.
Anyway, here is the link. I've printed and played the game, but I'm also purchasing 1 and donating two copies to OG.