Senketsu

A living sailor uniform Ryuuko finds beneath her house. Senketsu is a Kamui (神衣 lit. "God Clothes"), an outfit that provides its wearer with godlike abilities in exchange for their blood. He has the power to transform into an indestructible suit of armor, albeit with a skimpy appearance, much to Ryuuko's embarrassment. His name, given to him by Ryuuko, literally means "fresh blood."