Ace of Spades

[WeskerIncarnate]

http://ace-spades.com

Absolutely free sandbox FPS game that allows you to build random shit with blocks, be it fortresses, bunkers, trenches, etc., all while trying to capture the enemy team's intel in a capture-the-flag type scenario. Pretty fun.

http://www.youtube.com/watch?v=Sv8HQocOjF8

This is a much earlier build of the game, but it gives a good idea of what it's like anyway.

[Jill4EverSTARS]

Sounds awesome but tbh my first thougt was the song by Moturhead lol