Snowsong

Snowsong is Thrall's wolf companion.

Among the Frostwolf clan, all of the young warriors have wolves to help them hunt and survive. The orcs, in return, share their food with the wolves, heal their injuries, and protect their cubs. It is a relationship of equals looking out for one another, rather than the master/pet relationship one might expect. While Thrall was living among the Frostwolf clan, Snowsong chose to bond with him for life.

World of Warcraft: Stormrage
Snowsong also makes a short appearance in World of Warcraft novel Stormrage mourning her "hunting-brother" Thrall who has been claimed by the Emerald Nightmare. It's also Snowsong who first catches the scent of the shadowy invaders assembling outside Orgrimmar's walls, simultaneously alerting the defenders that the lookouts already have fallen prey to the Nightmare.

Speculation
It has been theorized that Snowsong is not the wolf Thrall is seen riding in Warcraft III, since the fur of Thrall's mount is black and Snowsong had white fur, although many species of wolf are known to change the color of their coat as the seasons change. In The Burning Crusade, Thrall travels through Nagrand on a white wolf, which is almost certainly Snowsong. In Wrath of the Lich King, Thrall can also be found riding a white wolf in.