I think something like an arena would be pretty cool.

well theres grey space, where you can fight and kill with no repercussions or faction loss. theres also the tubes where some fighting/killing takes place.

a while ago I tried to set up a "newb war" in sedina, where newbs would battle for cash and others could wager on the outcome, but newbs are a bit less than trusting when getting invites to grey space.