I've mainly only cooked Chicken and Vegetable stocks - for whatever reason I still haven't gotten around to trying to make a beef stock or a pork stock. I guess it's mainly because I seldom buy any red meat with the bone in it - and if I do, I usually cook the bone along with the meat itself (such as with a t-bone). I do buy a lot of pork, but again, not often with the bone still in it. I mainly stick to boneless chops if I do buy them, because I don't want to be bothered with the extra cooking time to make sure the blood in the bones are cooked through as well. Similarly I avoid roasts with the bone still in, such as a pork butt, since it increases the cooking time too much.
That said, our grocer does regularly carry shanks, and neck bones, so I suppose I should give these a try soon someday. In particular I've been kind of interested in doing an asian style pork broth with the neck bones, using some fresh ginger, cilantro, garlic, and onions.
My attempts at vegetable stock have been largely abysmal. What I wind up with looks more like dirty water with sediment in it - the solids left behind in the broth all tend go clump together in the bottom of the mason jars I'm storing the stock in - and it looks rather unappetizing. Flavor wise, it's never worth the trouble either.