In case you are wondering, I am still here and recovering from a recent debugging binge.  What was the toughest bug you had to fix?  For me, it usually involves odd multi-threading behaviors of the containers.  Of course, one time there was this fantastic piece of self-modifying code that was a real 'joy' to debug.  To put it simply, graphics data got converted into self-modifying code so it can be rendered fast without having to access slow page-flipping memory.  Fun to code but not fun to debug.