Growing up in England, I used to love collecting and playing "Conkers
I lived close to a park which had dozens of mature Horse Chestnut Trees. As my friends and I went back to school we would throw sticks up into the trees to knock down the prickly seed cases. The large nut inside is inedible, but we would dry them and drill a hole through the centre from top to bottom, thread them individually onto a shoelace and then as one person holds their conker still their opponent flicks their conker into it until they either miss or the laces tangle, the player to call strings first gets to take a turn. This continues until one of the conkers is smashed and the winning (conquering conker) becomes a oncer, twicer, thricer etc.
As an sadult I still collected conkers, but planted them around the park. By the time I left in 2006 four or five of my planted conkers had formed some nicely growing trees for future generations of "conkerers"