Two Sides to Every Tale (the achievement for doing all the 8.1 quests on both sides basically) gives a horse to the Horde and a wolf to the Alliance, which seemed strange at first until I paid attention. The reward for the achievement is, in lore, a stolen mount.
Alliance get the Ironclad Frostclaw: “Captured in the snows of Alterac Valley, this bloodthirsty hunter now roars for the Alliance.”
Horde get the Bloodflank Charger: “Stolen from the Arathi Basin stables, this fire-hearted charger now steeds for the Horde.”
This is an achievement for completing Zandalar Forever!, A Nation United, and both Tides of Vengeance achievements. So basically, do the Horde zones and their culminating storyline, do the Alliance zones and their culminating storyline, and finish both sides of the 8.1 war campaign. I did one Alliance zone before completing the A Nation United part, so I’m not sure if they changed in a later patch or just made it easier to for alts. (I’m still working on Drustvar and will do Stormsong Valley last.)
While I liked the wolf, I thought the horse was a bit of letdown until I realized it was stolen. Now I like it!