I first came across this blog post that quickly reviewed what they called “weird” weapons of Asian martial arts. I’ll warn you know over half of the videos on that post do not work. I don’t personally find anything obscure about Shuriken (aka Ninja Stars) or Nunchaku as they have listed but I do find the Urumi quite interesting.

Derived from the art of Kalarippayattu, a southern Indian martial art. In Kalarippayattu, there are four stages (Meithari, Kolthari, Ankathari and Verumkai) of training and a practitioner does not reach the Urumi until the third stage (Ankathari).

Here’s an excerpt from Wikipedia’s article:

The sword is a flexible band of steel three-quarters to one inch in width, and long enough to reach from the fingertip of one hand to the finger tip of the other hand when the hands are held outstretched, (usually about four or five and a half feet). It has a small handle with a cover. Often there are Urumis with multiple belts on a single handle, which makes it more dangerous to the opponents and wielders alike.

In modern times it is often made from used Band-saw blades.

Agility and skill are more important to a mastery of the weapon than strength or aggression. Twirling and controlling the urumi is a difficult and dangerous art, and is therefore taught only to the best pupils of the Kalari. Incorrect use can result in the flexible sword wounding its wielder, and great concentration is required during use, even by experts.

The Urumi is most useful to a warrior when he is alone and has to fight multiple opponents.

I couldn’t find info on what kind of damage this causes on the battlefield but described to be razor sharp. Looks this would have been a slow way to shred your opposition to bits. I also find this to be difficult to use against more heavily amoured soldiers.

Here’s an old video documentary someone posted on YouTube; although, I’m at work right now and haven’t had a chance to listen to the content. It does show the Urumi in action; obviously, there are other videos to view on the weapon as well.