More flavor and connective tissue than any other part. While the meatier hind shank is most used, the fore shank is not neglected.
Center cut Beef Shanks (photo specimen) are great for beef soups and stews. They include plenty of the most flavorful meat on the beast, and plenty of connective tissue for a rich stock. The bone is cut in slices exposing the marrow, and very little of your money goes for fat
Beef Bones can come from all parts of the beast, but those from the shank (photo specimen) are particularly good because they include some of the most flavorful meat and plenty of connective tissue. These are also very easy for the butcher to cut up on his bandsaw. In any case, what you're looking for is bones with some meat and tendons on them, and cut or broken to expose marrow in the center.