Horn of the Frostwolf Howler

The Frostwolf Howler is an wolf mount, only rideable by players of the Horde. It was formerly only available to players who had reached the exalted reputation with the Frostwolf Clan, but is now available to anyone who has the necessary honor.

It may be interesting to note that the Frostwolf Clan was named after this creature and that these wolves have a great bond with shamans.

Source
This item is a PvP reward, and can be purchased for from  in Alterac Valley and  in Hillsbrad Foothills. You need riding skill of 150. The wolf is white with a red saddle and blue armor.