Deer body hair and the hairs from the very top of a buck tail are hollow, very buoyant, and make an awesome medium for bass, trout, and pike flies. The ability to splay and spin these hairs means a vast array of streamers and surface flies. Spinning deer hair flies is probably one of the most artistic forms of fly tying there is. Some people tie flies that look like taxidermied bluegills or mummichogs. I'm not nearly that good, so I'll stick to my impressionistic fish catching patterns.