King Pin is a level 71 rare elite big ass penguin with approximately 14k health. He can be found on the two islands in southwestern Howling Fjord in several different locations which are indicated in red below. He is one of three rares located in this zone. The other two are Vigdis the War Maiden and Perobas the Bloodthirster.
This npc is part of the Northern Exposure and Frostbitten achievements. He drops Egg Warming Blanket which is a level 70 bind on equip cloth chest piece with a random enchant. Like other Northrend rares, he also drops Abandoned Adventurer's Satchel, which generally contains about 20 gold, a full stack of frostweave cloth, and often times a few crystallized elements.
Although he is elite anyone questing in the area shouldn't have much trouble downing him. He does a charge called Belly Flop and a melee attack called Flipper Twack. He also awards a very decent amount of xp for characters around his level.
Also, notice how incredibly freakishly large he is for a penguin.