Retired Mounts
Alpha Mount: Spotted Nightsaber
This mount apparently existed only during the alpha testing period, before WoW launched.
Early Epic Mounts
In Patch 1.4, these unarmored epic mounts were removed from vendors and replaced with the armored level 60 mounts that we have today.
Semi-Retired Mounts
These mounts are not technically retired; they can still be obtained on certain realms and in certain situations. But it's not easy!