Not sure if the developers intended to do this or if its just a glitch but either way I found it hilarious. Was in the middle of doing a Dark Brotherhood quest, riding through the woods on Shadowmere. I looked away for a sec, looked back and I ended up running over a cliff with a pretty big drop. When I smacked the ground Shadowmere whined, flew a good 30 ft and died while I just laid there next to the creek face down for a good 20 sec watching the horse's body float down the creek. Eventually my dude just stood back up and went on as usual.

Yeah your horse always breaks your fall for some reason. It doesn't bother me...unless its shadowmere!

I always thought shadowmere was essential. Maybe that was a mod I downloaded.