Arma 2, a game of command, tactics and damn right fun. I would say the best warfare simulation game thats out. Its no call of duty or bf2 if thats what your looking for this game is more realistic with many real vehicles air, land and sea.
Really nice graphics although a decent computer is needed to get the most out of it the prettiness, user created mods and missions aswell as a single/mutiplayer player campagin will keep you playing again and again.
Downsides theres a few bugs that need patching but nothing major that spoilt my play of the game.
On the upside its one of those games that is worth the money crack open a few tins and play against or with friends, closest ive seen to real life warfare in a game.