Duty Calls (from the folks that make Gears of War).
http://www.thedutycalls.com/download.html (http://www.thedutycalls.com/download.html)
Heh,Gears 3 better be the shizz.Cos it took over a year for Gears 2 to be playable.Bad,bad netcode.
That being said,I'll be giving it an extensive trial.
Gears single player is pretty good,though.