In my opinion, stones are best used on non-wild pets, as there simply is no other way to make them rare. However there are exceptions, those pesky sparsely spawned pets. For a flying stone, I would recommend using it on the Crow from darkmoon. If you were lucky enough to catch a rare of that, you'll want to look at your vendor pets, examine their abilities and pick one with the most unique move set. Hope this helps and happy collecting.