Ikkakumon

Ikkakumon is a Sea Animal Digimon whose name is derived from the narwhal (一角獣) and whose design is derived from the narwhal, the walrus, and the polar bear. It was discovered by the computer of an Arctic exploration base. Its thick fur and stout body are structured so that it can endure even the freezing lands. Its sharp horn is made of "Mithril", one of the rare metals, and the skin under its fur is just as hard. The portions of its soles where its claws attach are heat tops that are able to give off high temperatures at will. As such, it's able to maintain a tight footing when on ice, but it isn't able to move very nimbly. When in battle, it will intimidate the opponent with an impressive roar similar to a lion's.

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

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

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

Digimon World 3
Ikkakumon is only available as a Blue Champion Card with 13/13.

Digimon Digital Card Battle
Ikkakumon is a Champion level Water deck card. He appers in session two in Igloo City.

Digimon World DS
Ikkakumon digivolves from Gomamon at LV 22, and can digivolve to Zudomon. Ikkakumon also appears in Drain Tunnel.

Digimon World Dawn/Dusk
Ikkakumon digivolves from Gomamon at LV 21 with 70% friendship and digivolves into Zudomon.

Attacks 
 * Harpoon Torpedo (Harpoon Vulcan): Shoots its regrow-able horn.