[Wyody]

I might call it "The Pit".
And perhaps, instead of smilies, one can choose from a collection of medieval arms.
There should also be an olive-branch ... for when it's time for someone to make peace, give in, give up or keel over from exhaustion.
Of course, Admin and/or the moderator would have a boot and a blowtorch.

Concerning the area of rules violation - the mod would have a list of one-liners such as "personal insults are out of bounds" and perhaps a numbering system such as "That's 1" - which would not have to be issued at every violation but perhaps at every serious violation or succession of smaller ones. When someone receives the "That's 3" notice, their avatar is subjected to boot or blowtorch thus removing them from The Pit.
To avoid the possibility of a moderator over-reacting and thus ruining an otherwise acceptable debate, three opinions from other members would be presented to Admin for "higher-judgement" and the debate would continue at Admin's discretion.
And perhaps, as PDX once mentioned - some "Pit" debates could be sent into a "Cage" with actual bloodshed occurring!