6. The Michael Mann "Fork"

At one point a certain man named Michael Mann submitted two patches to Freecell Solver, one of which I accepted.
Then he explained his greater motivation:
At one point he was interested to write a Freecell solver, but first decided to search if one existed. He found mine in a Google search.
He saw in my to-do list that I wanted to convert it to Java, so he decided to privately convert it to C++ instead.
He started at version 1.4, and as I released new versions he incorporated these changes into his C++ version, and so until version 2.2 of Freecell Solver.
After he "came out of the closet" he submitted his C++ version (which was documented using doxygen), which I placed online for reference.
This is the single most amazing thing that happened to me in my professional life as a programmer.