WoW Trading Card Game on account of living in China, where they don't sell this sort of stuff. But I always love to see the special items from loot cards you can find in the TGC. I've seen people with the spectral tiger a couple of times, as well as a bunch of people with the picnic grill and even a dragon kite.
But with their latest expansion pack, Servants of the Betrayer (they come out with expansion packs right quick compared to Blizzard, don't they?), they've added a "super-common" loot card. Apparently every single booster box full of smaller booster packets is supposed to have two of these things, a "Papa Hummel's Old-Fashioned Pet Biscuit," so pretty soon we may find this sort of item becoming rather ubiquitous. You'll also be able to use it with each of the characters you play, rather than having to choose just one.
But what exactly does it do? As you can see in the pic above, taken from their website, it'll make your non-combat pet you have grow significantly in size, up to the size of a normal hunter pet. But for me the really exciting thing is that it will enlarge your hunter and warlock pets too! I've always wanted to have a hunter with a huge pet, much bigger than my actual character for roleplay reasons, but it seems this might even be an advantage in PvP and Arenas, too, if I made my wing-flapping owl so huge that other players can't see past it so easily, for example. Anyways, this might be the first loot card that is not entirely outside the average player's reach, and especially attractive to two popular classes, no less.