HardHead

HardHead is a virus from the Mega Man Battle Network series. When it is closed, it is invulnerable to attacks. When open, it becomes vulnerable, and it launches cannonballs towards its target. Those cannonballs can break panels.

HardHead
 HardHeads are gray when closed. When open, they become red.

HardHead2/ColdHead
 HardHead2 s are yellow when closed. When open, they become red.

HardHead3/HotHead
 HardHead3 s are light-blue when closed. When open, they become red.

HardHeadΩ
 HardHeadΩs are forest green when closed. When open, they become blue.