The Phasor Blast Wave Pistol
If mace isn't quite doing the job for you anymore, you might want to look into the Phasor Blast Wave Pistol, an "experimental" device which is intended to scare away animals, but its "high pressure complex sonic shock waves", which create discomfort, disorientation, and nausea, can also be used on people. In fact, the misnamed "Information Unlimited" carries a whole range of sonic devices, including the Phasor Pain Field Blaster; the Phasor Pain Field Generator (for crowd control); and the Ultrasonic Blaster (for blowing holes in metal — or cleaning jewelry).
[Via GadgetMadness]
