I'd say Chris Wanstrath (GitHub cofounder, http://defunkt.github.com/projects.html) is when it comes to hacking on awesome OSS projects. Rip, hurl, some cool emacs scripts, hub, repl, and plenty more.
I don't know Mr. Wanstrath specifically, but it really isn't about hacking awesome OSS projects. It's about feel and attitude. _why was footloose, insane, and absolutely fun.
Yeah, I know. Chris is a lot more sane and doesn't have quite as much of a "fun" attitude, but he has a pretty cool attitude.
I strongly recommend reading his keynote from railsconf 09. The first half is him totally mocking the whole "rock star/ninja" idea: https://gist.github.com/0a2655aed6a26fa15a02