When I was 9 I (and my friends) considered having "battles" where we hit each other with sticks to be one of the best ideas we've ever had. Our solution when a kid nearly got got hit in the eye with a willow switch ... was to ban willow switches.

We also jumped out of trees using a trash bag as a parachute. Luckily we had just enough sense to jump just under the "break a leg" height.