ARMA 2 Free is a free version of one of the most realistic battle simulation games on the market. The game focuses heavily on team cooperation and squad tactics. Many different vehicles and aircraft are featured in the game including tanks, jets and helicopters.
The major drawback to this version of ARMA 2 is the lack of support for HD graphics and user created mods. Another downside is that the single player campaign is absent in this free version. Despite the drawbacks, the game is definitely worth trying if you don't want to shell out for the standard edition.