Do you currently own a Black Tabby? If you are an Alliance player be prepared to pay a hell of a price . If you are horde however this is a great pet to farm. I've managed to farm this pet with an alt 3 times in the last couple months. Twice I have sold this for between 600-1000g each. (600g horde side 1000g on neutral ah).The third farm however will probably be addressed in my upcoming "mistakes" post for the JMTC blogging carnival.
This is a great pet. A little history note the Black Tabby used to be know as the Maine Coon (see pic below for a real Maine Coon). This name was changed to Black Tabby due to the name being offensive (At one point in time had a Maine Coon and this is still the name of the breed). This is also one of two cats (the other being the Bombay) that Stinker the skunk will chase around lovesick like a crazy loony toon character.
It's easy enough to farm if you have a level 30 toon horde side, simply station them at the steps in Ambermill and create a macro that reads (/target Dalaran Spellscribe).
The Spellscribe will drop this pet about 27% of the time and spawns about once every 2-3 hours (some say 4-5). not a lot of people farm this and if you are able to Snag the cat it is worth 1000g on most of the servers out there. This is a great Halloween pet so heck who is to say you won't get more for it this time of year.
Good luck and keep making Gold!