Out in the playground would be the usual arena for a good old game of conkers or marbles.
Your prize conker in hand, stringed up and ready for competition, giving it a good swing and ‘whack’ against your opponents conker until one eventually gives way! Then searching for your next competitor, or perhaps he would already be waiting, ready to test his own champion chestnut!
Just watch out for the dreaded ‘stampsese’!!
Marbles is a less aggressive sport, though far more challenging.
If you’re playing with your best marbles, don't play for ‘keeps’!!