Behold, the most ridiculous glitch in the entirety of Skyrim: Horse tilting.
Image source: Skyrim wiki
Yes, you read that right. Horse tilting. One of the many strategies used in modern Skyrim speedruns involves making a couple of saves, and then tipping a horse over on a rock. If done correctly, your character will start running and flying at mach speed, as you'll see in this tutorial video by Fivexual. (You might know him as the current world record holder for beating Skyrim as fast as possible AND for getting married as fast as possible in Skyrim.)
"You kind of want your horse to be sinking, as if it were quicksand," Fivexual explained. "That usually means that you got the tilt and you can get off the horse."
I think the best part about this glitch is that what you see in the video is apparently one of the slower speeds you can trigger with horse tilting.
"The speed is determined by how far, or how close you are from the horse," Fivexual said. As you can see in the video, Fivexual saves rather close to the horse. "The farther away I am to the horse, the faster I'll move, the closer I am, the slower I move."
You gotta love Skyrim.