I believe, in a modern day firing squad, some of the shooters have blank rounds (was on some type of Nat Geo show)... this way none really knows who fired the killing shot. I could be wrong tho..
It is an old game now, but GRAW 2 does split screen online coop and vs (and GRAW1 if you wanna go back even further.) I have it on xbox360 so Icannot speak for the PS3 version, but I go back and play the coop missions all the time and there are still people playing. 1 negative, and its been...