The Dothraki Arakh
The arakh has a crescent-shaped blade and a long handle. Visually, the weapon falls somewhere between a sword and a scythe. Used most mostly by the Dothraki warriors, the arakh's design allows for a vast sweeping motion.
On Game of Thrones, Jorah Mormont comments that the blade works best when the fighter is on horseback. However, the arakh is no match for a Westerosian double-edged sword in hand-to-hand combat and cannot penetrate armor.