Ninja Gaiden Dragon Sword stylus, which he received at a Tecmo party. It's a little sword! With a scabbard and everything.
Sure, poking at the touch screen with a plastic finger is okay, but the idea that we could advance through Elite Beat Agents by repeatedly stabbing and slicing at the title characters is disturbingly irresistible. Wait, that came out wrong. We can, and quite frequently do, resist the urge to stab fictional characters.