Meet the Wasp Knife. Wasp Knife's creators had a problem. It seemed that boring old traditional knives weren't quite deadly enough, so they decided to evolve the long-standing design and put a compressed gas cylinder and firing mechanism into the handle.
The Wasp Knife is designed to fend off marauding sharks and hungry bears, and mainly aimed at divers, downed pilots, lost hikers, etc.
This is how it works: after taking all necessary precautions to avoid unwarranted animal protection groups haranguing you at a later stage - possibly by first letting the predators have a nibble on your least favourite limb - you can then insert the blade into your attacker. Next you depress a conveniently placed button delivering a frozen ball of compressed gas through the blade which inflates to the size of a basketball (!) and freezes your target's organs.
Hit the turn for a video showing what stabbing a harmless watermelon with a compressed gas empowered knife does for you.
From: Apple tease Galaxy Note owners with iPhone stylus patent application