Personally I’d say cave diving. I was contemplating between that and free climbing soloing but I honestly rather fall to my death than drown in a claustrophobic, dark, cold, silted up cave.
Anvil firing
You get 2 anvils, stack them on top of each other, the bottom one upside down, pack some gunpowder between them, light it, run, and the top one shoots off into the air and eventually comes back down.
I’m sure it’s a blast (literally) but I’m not trying to looney tunes myself.