Kind of trollish question, and I wouldn't even dare to try to answer it as there's so many people in this community doing great work.

But I'll give one example off the top of my head, of someone who impresses me: thp. I haven't read his code or even tried most of the stuff he's done. But I'm nevertheless impressed, because 1) he's done lots of very different great stuff 2) most of it is open-source.