Fortune Coin

The Fortune Coin item summons and dismisses Lucky, a golden pig Companion. Occasionally, Lucky grazes on weeds and wiggles its rear.

Source
Participants of the Blizzard Worldwide Invitational 2007 were given a code that unlocks this pet in-game. The item can be acquired from the following NPCs by redeeming the WWI promotion codes:
 * in (Ironforge)
 * in (Orgrimmar)
 * in (Shattrath City)

Inspiration
2007 was the Year of the Golden Pig. Those born in The Year of the Golden Pig are supposed to be wealthy, prosperous, lucky, and fertile.