ResEdit was an incredibly cool tool, with a surprisingly good (and intuitive!) interface for what was clearly a developer tool. I started using it to poke around in games when I was around 9 years old -- admittedly I didn't understand everything I saw, but there was still a lot of interesting stuff to see.
ResEdit was one of the things that got me hooked on programming because it was (1) so accessible and (2) could be used on real executables.
A few months after discovering it, I had jammed little hand drawn icons onto the menu items of damn near every application on my tiny hard drive. It was awesome.
I bet there's a whole slew of us who spent countless hours inspecting everything, trying to take it all apart... that formed the developers we are today.
