The Piko Piko Hammer.
The Piko Piko Hammer is Amy Rose's signature weapon, gained after she made herself older by wishing on the Ring of Acorns. Magically, the hammer first came to her by materializing in her hand while trying to protect a Flicky that was being hunted by Dr. Eggman's E-100 Alpha robots. Despite its cute appearance, it is incredibly hard and durable, as it is able to easily crush entire robots into pieces with one swing. It is also capable of deflecting projectiles like bullets and Shadow the Hedgehog's Chaos Spear. However, it is not indestructible, as Rosy the Rascal was able to break it with her version of the Piko Piko Hammer (which could be considered the Anti-Piko Piko Hammer). Amy has used this in every battle she has been in with incredible proficiency, either through natural talent, or through an unknown amount of practice. (StH: #81, #194, CSE)