Through the "archaeology" skill, I've managed to dig up a Fossilized Raptor. Yes, I can ride on a museum exhibit. Creepy? Cool? You be the judge. 
There's a 5-man dungeon called "Magister's Terrace". If it's run on 'heroic' mode (enemies are more difficult, loot is more impressive), it can only be run once a day but the final boss has a TINY chance of dropping the Swift White Hawkstrider (sometimes affectionately referred to as a "battle chicken" or a "thunder chicken"). Not only is there an achievement for having it, hawkstriders are the racial mount for Blood Elves in the Horde faction. Thus, for an Alliance toon to have one is a bit of a bragging right. I've run in there alone and beaten his sorry ass every day for a month...and he finally got the hint and gave me the bird. ;)Now, to get ONE MORE MOUNT. Hmm...methinks I should spend today beating on Baron Rivendare, and force him to drop his Deathcharger...and, just because I happened to have the screencaps around...
Quel'dorei Steed
An elven equine mount, bought with marks earned from competing in the Argent Tournament. Funny, I'm hanging out not far from the above-mentioned dungeon.
Albino Drake (awarded for having 50 mounts in your stable)
There are many drakes in the game of varying colors. I also have a red one and a bronze one, but this one is cooler.