I remember when I was about 7 or 8, we used to take our Red Ryder BB guns, remove the BB sized barrel and shroud to where there was just the metal outer sleeve left, pump them up about 50 times, and shoot rocks at each other, usually from point blank range.
Then one of our moms would ask what we were up to out there, we just answer "Nothin, just playin' army."
Really puts an end to those annoying "I shot you!" "Nuh-uh, you missed!" arguments.