Several mounts are available from the World of Warcraft Trading Card Game. You can get these mounts by finding rare cards in the game, and turning in a code that is on the card. These mounts have been known to go for upwards of $600 on ebay.

Riding Turtle		Spectral Tiger
Speed: 0% Minimum Level: 20 Riding Skill: 0		Speed: 60% Minimum Level: 40 Riding Skill: 75
Swift Spectral Tiger		X-51 Nether Rocket
Speed: 100% Minimum Level: 60 Riding Skill: 150		Speed: 60% Minimum Level: 70 Riding Skill: 225
X-51 Nether Rocket EXTREME
Speed: 280% Minimum Level: 70 Riding Skill: 300

WoW Insider's Guide to the Mounts of the World of Warcraft
Table of Contents		Index