A knife is a relatively simple tool — a piece of solid metal (or some other hard material) with a sharp edge and sometimes a piercing point. Other details such as the metal composition, heat treat, and blade profile will dramatically affect its durability and cutting performance, but at the end of the day it's still a sharp piece of metal. However, over the years, a few designers have tried thinking outside the box to develop knives which can deal more damage to a specific type of target.

A few of these unconventional knife designs have utilized compressed gas. Ballistic knives, for example, have used compressed air or CO2 to fire a blade a short distance from the handle. Outside video games and movies, the effectiveness of ballistic knives is dubious to say the least. But there's a second type of knife that uses compressed gas — the injection knife.

The WASP Injection Knife is designed to inject high-pressure gas into a wound cavity through a hole in the blade, rather than using gas to propel the blade forward. This is said to expand and freeze the wound, inflicting more damage to the target. On WaspInjection.com, the knife's manufacturer states:

“This weapon injects a freezing cold ball of compressed gas, approximately the size of a basketball, at 800psi nearly instantly. The effects of this injection will drop many of the world's largest land predators. The effects of the compressed gas not only cause over-inflation during ascent when used underwater, but also freezes all tissues and organs surrounding the point of injection on land or at sea.”

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These are some bold claims, but how does the knife's injection system fare in reality? Unsurprisingly, there doesn't appear to be any video footage of SCUBA divers stabbing sharks with the WASP, but several YouTubers have tested the knife on ballistic gel, plastic bottles, and watermelons to show how the system works:

More videos of the knife in action are available here and here. One downside to this knife is that it can only inject CO2 once before the handle must be unscrewed and a new cartridge must be installed. Also, it'll set you back $500 for standard models, or $600 for the larger WASP Bowie model.

So, what do you think of this unconventional injection knife? Tell us your opinion in the poll below.