I have not read all the posts in this thread but am sure mine will be unique.
3 years ago I spent time with my 8 & 10 year old grandsons in Virginia, we built a coaster car out of scrap lumber. Instead of old mower wheels and axles, I found some nice ball bearing wheels and axles that rolled much easier. Too easy it turns out. Rope steering completed the vehicle.
The boys took turns coasting down the gentle side of the hill in front of their house on the road. It was so much fun that even old Grandpop tried it out. it was a lot of fun.
Later we tried the steeper hill going in the other direction. Oldest grandson started half way down the hill, it was faster and more exciting. I figured that if a 9 year old could do it, I surely could (dumb mistake). I ALMOST made it to the bottom of the hill before rolling the car over as I aimed toward the edge of the road to run onto the grass.
Besides scaring the crap out of my grandsons and daughter, I cleaned out the antiseptic spray and bandages they had in the house. I slept in the recliner at home for 3 nights until I could lay in the bed without hurting myself. Never again, well, until next time.