Mammoth mounts

Mammoth mounts are vanity mounts that were added in Wrath of the Lich King. Some can accommodate passengers, and they all (currently) have subtle (and sometimes not so subtle) shadings for each faction.

Exotic mounts in Dalaran
These Wooly Mammoths are available from Mei Francis in Dalaran for 200 Emblem of Heroism.

Wintergrasp Mammoths
There are two sets of Mammoth mounts available from Wintergrasp.

The first are the Black War Mammoths, available from the Wintergrasp quartermaster for the respective faction (requiring control of the Wintergrasp keep for access), at a cost of 300 Stone Keeper's Shard.

Sons of Hodir mammoths
If you are at least with the Sons of Hodir, you may purchase the Ice Mammoth mount from the Sons of Hodir quartermaster in Dun Niffelem in the Storm Peaks for.