Riding a unicycle on flat firm surfaces is hard enough, using one off road and down hill, is a sure recipe for pain and humiliation. The forward flip into water still hurts when it goes wrong. A Hoverboard is a never ending source of embarrassment and injury, and arm wrestling your grandpa and losing is just plain wrong.
Stacked push ups will reach a point where gravity causes pain and humiliation. Dive bombs are pretty scientific, get it wrong and it will hurt. Animals and objects are always good for humour. Frisbee golf is great fun, but ignore the science involved and a lot of agony and embarrassment will result.