Realistically, a knife so I can kill myself and get it over with. The mephitic miasma generally attending such events is unlikely to be kind to an asthmatic....
Semi-realistically, a Guan Dao; the kind with a stout spike on the back end. Against a straggler, either aim for the neck, or chop the legs and then bust his skull with the back end. Against the horde, chop the legs to slow 'em down, then run; holding your ground against the horde is suicide, pure and simple. Alternately, a Spartan shield. Made for both offense and defense, you can knock or push the enemy back with the flat, or crack skulls with the edge.
Unrealistically, I want Hawkgirl's Nth metal power mace from JLU. If it can knock Solomon Grundy across a room, it can damn sure take care of some pissant brainmunchers.