Combine a CO2 injection system into the blade of a knife and you get this: www.waspknife.com

It's a knife specifically designed to pierce skin (human or animal) and end life by injecting frozen compressed Carbon Dioxide (kinda redundant as compressed CO2 is friggin cold, regardless) into the organs to freeze/expand them.

Yikes.

I'm all for keeping up to date with intentionally non-lethal deterrent devices (tasers, sonic scramblers, light amplification shooters, etc) but this is a whole new realm of nasty.