I guess I do tend to use systems in unexpected ways, and I get some satisfaction
  when this reveals a flaw. For example, I remember having fun while visiting my
  sister and playing with a `shoot-em-up' game that my nephew showed me.

  Since I'm kind of a pacifist, I tried shooting bullets at the wall, instead of
  trying to kill the hidden attackers. Sure enough, I could spell my name on that
  wall, by making bullet holes in an appropriate pattern. But later when I came back
  to that same position, after wandering around further in the game, my name was gone!
  I think that was a bug in the software.

I love this. Especially the fact that he wrote was probably doing the only thing he wanted to do in the game, and was foiled by the fact that the game programmers didn't dedicate extra memory to saving environmental damage throughout a level.