Moldorm

Game - A Link to the Past

Dungeon - Tower of Hera

Weakness - Sword

Prize - Pendant of Wisdom

Moldorm guards the Pendant of Wisdom in the third dungeon of A Link to the Past. He moves around his platform and tries to push Link over the edge. But Link can defeat him by hitting his tail with his sword. After it is defeated, Link gets the Pendant of Wisdom and a Heart Container.

Later in the Tower of Ganon he guards the way up.

Moldorm appears as a regular ememy in The Minish Cap. Quote from The Legend of Zelda: The Minish Cap Moldorm figurine:

"Appears in various areas. These guys move quickly and randomly. Trap them in a corner and take them out quickly."