I'm a big fan of 'toss the AI impact grenade'.
Sure, it's not a real game, but it can be fun if you have a few people and you're waiting for others to gear up.
One of the best games I've played was tug of war over a hostage. The hostage gets to screw with everyone (running away if left undefended) and both teams compete against each other. It works best when the hostage cannot completely die, but can be incapacitated for a few minutes when shot.
Last edited by Jaelommiss; May 15th, 2012 at 22:28..