This is the Spectral Tiger from the World of Warcraft trading card game. For those that missed it, this is one of those prizes you get from getting one of the random, and very rare, loot cards. By keying in the code from the card you are allowed to purchase this mount.
I have to admit after finally seeing one in person I was underwhelmed. The armor on the tiger just doesn't look right. Either the armor needs to go, or it needs the same level of transparency.
If I'm lucky enough to stumble on one of these cards, It's going to Ebay.
Now about that rocket mount ...