Go! Projectile... Something!
It was a square item that was handed to Yachiru before she and her beloved Ken-chan went out to battle Hollows. It was called a GPS. Apparently it had the ability to tell you where you were in the world, and how far, and how to get to your destination. Yachiru wasn't too sure anymore, she kinda fell a sleep during the Shinigami Women's Association meeting about the thing. Something about how boring the frame and screen saver was.
Well, what ever it was, it was good at cracking Hollow masks in half when it was thrown like a projectile.