ArmA 2 is available on Steam today, and the very co-op friendly game is already getting fairly solid praises. While the game sports a robust single player and co-op campaign, as well as plenty of online options - it's the mission editor of ArmA 2 that's getting a lot of attention.
Why?
I'll let this video do the talking, as they say - a picture is worth 1000 exploding planes.