We supposedly try not to kill each other while playing (unless thats the point of the game, in which case we're terrible at it):

Team Fortress 2
Aliens vs Predator
Grid
Dirt 2
Need for Speed: Shift
Need for Speed: Hot Hirsute
Left 4 Dead
Left 4 Dead 2
Portal 2
Half Life 2: Deathmatch
Killing Floor
Mount and Blade (though it only works on LAN. Boo!)
Worms Reloaded
Magicka
Terraria
Serious Sam 1 & 2
Splinter Cell Conviction
Borderlands
and the odd game of Minecraft here and there.

We're pretty OK about killing bots though. sadface.