The Death Giant (MMIII) has a "nice" little aura that forces anyone within 15' what is on 10 or fewer hit points to make a fortitude save or die.
The first question is "What can we do to make the aura larger?" E.g. 30' could be really nasty, but I am not aware of a Widen SU feat.
The next question is "What else has a similar aura?" I.e. kills close enemies on 0 or fewer hitpoints. (I am only really after killing 0 or fewer so the DG's 10 or fewer is a bonus.)
There was a related question "what types of corporeal undead can blow a horn of fog?" as skeletons should not be able to, but then I realised that an eversmoking bottle might do me better.