This is a video of two guys performing a choreographed battle with urumi, or metal whip swords. How they both didn't cut their own legs off is beyond me, but I suspect they're trained professionals and not just two guys they picked up off the street and offered $20 to kill each other. Per Wikipedia:
The urumi is a sword with a flexible whip-like blade from India. Originating in the country's southern states, it is thought to have existed as far back as the Maurya dynasty (~322-185 BC). The urumi is considered one of the most difficult weapons to master due to the risk of injuring oneself. It is treated as a steel whip, and therefore requires prior knowledge of that weapon. For this reason, the urumi is always taught last in the Indian martial arts.
Obviously, I just ordered some urumi online and have every intention of challenging my roommate to a battle to the death. What he doesn't know though is his urumi is actually just going to be a strip of cardboard covered in tin foil. Provided I don't accidentally kill myself, I think I've got this.
Keep going for the video, then go grab a metal tape-measure and practice yourself at home.
Thanks to Dunc, who informed me there are actually urumi with MULTIPLE blades, making them even more dangerous. Just kidding, he didn't tell me that, I just saw a picture on Wikipedia.