The Lightning Barrel is a tool that allows the user to shoot lightning from it. To activate it, the user must tap the barrel against the ground. The barrel will then shoot one bolt of lightning. As explained by Kakashi Hatake, this is used to give away a user's position so their team-mates can regroup with each other. Another use that is shown is the ability to shock others by aiming the barrel at the ground, Although this might have been just Kakashi flowing his chakra through the barrel to the ground.