Mysterious Shell
Mysterious Shells appear in The Legend of Zelda: The Minish Cap. They serve only one purpose, namely buying figurines from the Figurine Shop (Found in Hyrule Town). They are found all over the Minish Cap world, in things like chests, blades of grass, and even rocks.
They are similar to the seashells found on Koholint Island in Link's Awakening, which can be gathered to obtain the sword upgrade, as well as pieces of heart.