America's Army is one of a few video games the DoD has put out as recruitment tools. They're a little weird (both sides always see themselves as US troops, fighting an unspecified opposing force), but I'm not sure how successful they've been over the years.
Another interesting one is what Bohemia Interactive does -- they develop and commercially release simulation-style shooters in the ArmA series, and they developed the original Operation Flashpoint back in the early 00s. But Bohemia also has a product they sell to armed services around the globe. It's gotten them in trouble before -- a few developers were detained in Greece while gathering reference material for the fictional island of Altis in Arma 3.