We make soap from our elk and deer tallow, although the fat that renders out from the bone marrow when you're making stock isn't as hard or high-quality as the true tallow that's deposited on the body. Gotta render that down separately. The marrow isn't half bad if you can cook it on its own though, just gotta eat it piping hot on good bread to keep it from waxing up your mouth - red wine or whiskey help with that too.