Using the Digi-egg of Reliability, Metalmon can Armor Digivolve into Narwhamon, an Armor/Champion/Ultimate level digimon. Though it may be half the size of normal Whamon, it's twice as powerful, and a tough competitor among the sea dwelling digimon. It's plated armor and sharp horn make it one whale you wouldn't want to mess with. It's signature moves are Harpoon Rush, Tidal Crusher, and Javelin Storm.
Credit for the sprites used to make Narwhamon go to the guys at WithTheWill.net.
Credit also goes to the creators of the Digimon franchise, for without them all of this would not be possible.