I usually roll around on my 60/60/60 war tiger (I know the removed the mark requirement but don't know a better way to describe it) on ground
Frosty or Magnificent flying carpet on flying. Can't really tell the difference in shadowform though so I usually just roll Frosty and use Magnificent for my Disc spec.
I want Baron Rivendare's mount though for my ground mount as I rolled around on the undead mount when I was horde....