no killing each other off without permission 
this roleplay is rated M
there can only be 1 [we all gotta die eventually]

Arguing points: 

-It is an HGRP IT IS PVP HOW IS IT WE NEED PERMISSION TO KILL??!

-Roleplay rated M? Doubt that 

-only one person left, then don't do "permission to kill" if you want the RP to end.

There are my two cents.