Seen here in stabby mode, this is a video of knifesmith and Youtuber Kiwami Japan creating a functional knife from a roll of plastic kitchen wrap that he melted, molded, and sharpened (previously: forging knives out of aluminum foil and fish flesh). The end result is fairly functional, although it doesn't slice clean through vegetables like a ninja sword and requires some sawing action. *shrug* I guess everybody needs a hobby. And in this man's case, it's clearly thinking of clever ways to protect yourself in the event of prison.
Keep going for the video.
Thanks to speakerbox, who wants to see a functional knife forged out of air.