Some classes get special mounts that no other classes can have. Most of these mounts can be purchased from your class trainer, although the two Death Knight mounts and the Argent Charger are exceptions.
Click on a mount to learn more about it.
Level 20(Draenei) (Tauren) (Human) (Blood Elf) (Dwarf) (Dark Iron Dwarf)
Level 40(Dwarf / Human) (Blood Elf) (Draenei) (Tauren)
Druids do not receive class mounts, but they can purchase flight forms that provide the same functionality as a flying mount.