After my Barley 3rd Star Power idea, I've decided to make some more idea star powers.
Shelly's third star power: Boom!
Shelly gains a Boom bar! The Boom bar takes 3.0 seconds to charge when Shelly is not using any of her three ammo bars. When you fire your first attack with the Boom bar, each shell does 15% more damage. (483 damage per shell)