Me:
At my school World War I/II games (at ten, they sort of blended together for us lol) were king.
We had a trench of sorts, a drainage ditch with cement, and when it was dry and on a summer day that thing became a cannonade trench with the guys there on the "heavy artillery" (basketballs, soccerballs, volleyballs, etc.) and the other side charging "rifles/pistols" (tennis balls or dirt clods or whatever) hurling them.
Sometimes it was like freeze tag with the balls, or get hit and you're "down" for the rest of the "battle..."
Good times... we went up and down that field all the time, great exercise... sort of like capture the flag (actually, it was "Capture the Backpack," we had no flags lol) but it instantly with that trench and the "artillery" and "rifles" became Axis vs. Allies on the playground...
I still remember when we were divying up teams how folks wanted the "accurate" guys or the "fast" guys or the ones who could duck the best and avoid getting hit to "keep the line going" (I was good at that...)
DAMN! Kids today don't know what they're missing... just a decade ago we had great, exercise-buddy games like this, now its all "Call Of Duty" for kids...