I suspect i might be the winner here. My friend had an alley behind his house along with a nice strip of open land near a busy road. Eventually a strip mall was built and then another large commercial building started to go up. Being basically behind my friends house we walked over to this new building on weekend to check out the construction site.

The building was being built with cement block and had lots of scaffolding and yet-unused block scattered around. I found a pipe-bender - a very heavy tool made out of high quality steel - and found you could just tap on of these cement blocks and it would shatter to pieces. I was fascinated, as were my friends. I have no idea how many cement blocks we destroyed over the next couple of days, but it was a huge number. Then we decided to see if we could go through a wall with the pipe bender... we could indeed, making a hole in the side of the building we could walk through. Looking around we eventually realized what we'd done was awful.... we had decimated this construction site. We finally slinked away and come Monday when the crew returned, police were called and neighbors interrogated but thankfully with privacy fences all around, none of the neighbors saw anything. 11 and 12 yr olds are stupid.