All of these games, would require that you have your @fatal off, and not kill (only KO) your opponents (since we clone, and don't respawn), though a deathmatch version might also be fun.
Here are my ideas.
Capture the flag
An assortment of PC's and a few NPCs on two teams. One in the Sinner Base, one in the Artery base. The flags would be weighted like the mini-gun and would reduce your dodge, and prolly only be used as a melee weapon. You would also move slower, and the goal would be to get the opponents flag to your base, at which point you would win.
Skull
There is a skull, it reduces your movement speed. You have to hang on to the skull for a certain amount of points, points adding up every 10 seconds or 1 minute that you have the skull, not sure exactly how. An OOC annountment would be made every minute of where the skull was, and the points of everyone.
Bloodtag
Already been played ICLy, but this would be more rampage style. one person gets tagged as 'it'. The goal is to kill that one person. OOC announcements would be made every minute or so telling you where the person was, and they have to run/jump/hide for as long as they can. (No stelathing).
Siege (Players vs. NPCs)
Players hold up in a specific area (say, the drome) and have to hold off hoards of NPCs for as long as possible.
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If you guys are interested, I'll put some code in on these, perhaps even tomorrow and we can give them a shot.