Boards
Ace Of Spades (it's a game)
this is great, the most fun I've had playing a game in a long time, it's free, and it'll run no matter what crappy pc you have.
It's like minecraft with guns, you build trenches and forts and stuff as well as try to capture the enemy intel and defend yours.
Here's a picture thing that explains stuff http://tinyurl.com/6ds3vbm
and here's a link to the game site (it's very basic, the download is only a few MB)