Stallman: "I have nearly finished the optimizing C compiler and all the other software that is needed for running C programs. This includes a source-level debugger that has many features that the other source-level debuggers on Unix don't have."
He refers to gcc and gdb:
http://en.wikipedia.org/wiki/Richard_Stallman
"Stallman has also developed a number of pieces of widely used software, including the original Emacs,[5] the GNU Compiler Collection,[6] the GNU Debugger,[7] and various tools in the GNU coreutils.[8]"
That's one successful hacker.