A teen prank that was popular here about two summers ago -and I heard and saw the effect on my neighbor's mail box -was to put dry ice in a plastic pop bottle, add water, shake briefly, screw the cap on, throw it in a mail box and run like hell.

It makes one helluva boom (woke me from a sound sleep), and seriously deformed a sturdy metal box. Apparently the police caught the small group that was doing it, and the fad passed away.