You've all heard of it I'm sure, and you're thinking "A game released by the US government, talk about open brain-washing", sure, it probably says join the Army every 3 frames, but its a great game and its free.
If you have time (even if you don't) download it at
AmericasArmy.com (650 MB). Its a full-game, like off the shelf, its basically Counter-Strike with decent anti-cheats and more realism.
Its a pain in the dick to get started (basic training and all), but once you get it done, you get a variety of new toys, including AK-47u with mods, and M4A1 SOP MODS.
Try it, you'll like it, I'll post a few screenshots later on, I'm going to bed, night.
added screenshot of me after being mowed by wacki iraqis;