More than likely there are/is a file(s) in your home library's preferences folder, as well as stuff in the application support folder. Just do a spotlight search for things like "wow", "warcraft" and "blizzard" and you should get it all.
Google AppTrap, after installation, all you need to do is drag the app to the trash and it automatically searches for any additional stuff to delete, then it asks you if you want to "move" or "keep", it's not completely fool-proof though.