Ikkakumon

Ikkakumon is a Sea Animal Digimon. His name is derived from the Japanese word "ikkaku", which means single-horn. He is a large, furry, walrus-like creature with a horn on his head and paws on each foot. His fur can withstand the coldest of lands. When he's not moving, his giant body is like a white gun platform.

Digimon Tamers
Ikkakumon is one of the shadowed Digimon who wanted Rika to tamed him as a Partner.

Digimon Savers
Ten years before the events of the series, a Gomamon emerged from the water and Digivolved into Ikkakumon where it attacked Suguru Daimon's group (it had enraged after Kurata shot at one of the Digimon).

Digimon Adventure V-Tamer 01
Gon the Gomamon Digivolved to Ikkakumon after being appointed the new Net Ocean Protector by Lord Whamon.

Digimon World 2
Ikkakumon digivolves from Gomamon and Penguinmon, and can digivolve to Whamon or Zudomon.

Digimon Digital Card Battle
Ikkakumon is a Champion level Water deck card.

Digimon World DS
Ikkakumon digivolves from Gomamon, and can digivolve to Zudomon. Ikkakumon also appears in Drain Tunnel.

Digimon World: Dawn/Dusk
Ikkakumon digivolves from Gomamon (which digivolves from Poyomon). The easiest way to obtain it is to degenerate (de-digivolve) a Zudomon (Zudomon appears in the Access Glacier area after completing, "The Combat Game" - Machine Quest).

Attacks 
 * Harpoon Torpedo (Harpoon Vulcan): Shoots out several horned-shaped rockets from his horn, each one opening and revealing a small torpedo inside.
 * Icicle Coat: Thin icicles sprout from Ikkakumon's body, freezing enemies around him.
 * Belly Flop: Jumps in the air and falls on enemies with his belly.
 * Horn Attack: Attacks with his horn.
 * Heat Top: His horn becomes very hot and he strikes opponents with it.