would be a scientist (auto-didact, if that excludes him for you) and is among the youngest people I can think of given your restrictions (31). He has written a few very interesting pieces on AI (Warning: Transhumanist/Singularitan), as well as the best Harry Potter fanfiction I've ever read: http://www.fanfiction.net/s/5782108/1/Harry_Potter_and_the_Methods_of_Rationality
For more information see: http://yudkowsky.net/ http://en.wikipedia.org/wiki/Eliezer_Yudkowsky
May I suggest though not to restrict yourself to actual people? "Hero" is a word I use extremely rarely, since I consider that to be a "larger than life, thus fictional" label...
Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (10) Sorry, but that's too useful.