A good friend of mine goes elk hunting just about every year. This past year he gave me a chunk of elk hide and elk knee for tying flys. The elk knee (after I shampooed it with Dawn) cleaned up very nice and had a great array of colors. Here's a pic:
And if you look at the flys on the upper right, these are all "elk hair caddis" flys tied with the elk knee he gave me. Of course, my friend will get his share of flys as well.