Built a treehouse and lived to tell about it
Spent the last 4 weekends building a treehouse in the oak tree with my 8 year old. He hammered half the nails, I made sure we didn't die. We christened it yesterday and he said it's the best day ever. Totally worth the splinters and almost dropping the 2x4 on my foot twice. Planning to build a rope bridge next which my wife thinks is insane but I'm thinking it could work.
Living to tell about it is the key part lol. Building something like that with a kid is way harder than doing it solo but also way better. Those are the stories they tell their kids someday.