Worg Pup

This is a great pet, and pretty rare from what I've seen. Not hard to get at all, but a little annoying, as you have to trek through Lower Blackrock Spire to kill Halcyon (you don't have to do a full clear thankfully)

The quest to get this pet (and another pet as well, the Smolderweb Spider) is given by Kibler inside the cave at Flame Crest in Burning Steppes. http://www.wowhead.com/?quest=4729

The pet itself is a bit larger than the usual critter pets. It also randomly can be either Brown/white or black in color. This has no relevance to which of Halcyon's pups you cage, it is simply random when you summon the pet. If you want the other color, simply dismiss and summon again as you have a 50/50 chance of getting either.

I think all the unique factors make this into an excellent pet to have. Good luck.

The pup is still in the game. It just dropped off of the Quartermaster for me, not far from Halcyon.

The quest to get this companion has been removed from the game. Unsure if this companion will be obtainable by other means once Cataclysm is released.