The Physical Jew

[Alex K]

I'll start with the man my PhD advisor called probably the smartest person he's ever met

Steven Weinberg

You might know him from some pithy quotes about religion and atheism. He is the central architect of our modern theory of fundamental interactions, the guy who recognized the real importance of Peter Higgs' idea and put it to use to explain the masses of fundamental particles. Really, he's the one who (co-)invented the actual theory, not Peter Higgs. Higgs came up with the basic idea, but in a simpler form and not in the context in which it is used today  - alas, Steve Weinberg had already gotten his Nobel Prize in 1979 soon after the discovery of the effects of the Z boson (along with his friend, the lone muslim physics Nobel winner Abdus Salam, and Sheldon Glashow, on whose ideas Weinberg based what is today known as the electroweak standard model of particle physics), so he wasn't going to get it again for almost the same thing.
Not only did Weinberg construct the Higgs model, he also invented the leading rival theory, which was investigated intensely until it was ruled out experimentally. Talk about covering all bases. When I worked at the theory institute in Heidelberg, my boss was working on some conceptual cosmology issues, and Steve Weinberg, then almost 80 years old, was right there on the leading edge, thinking about infrared singularities in big bang cosmology and similar mind-numbingly complicated things.
In fact, besides his crucial work on fudamental interactions, Weinberg was a leading contributor to our modern ideas about cosmology and the unification of gravitation and quantum theory. One of his ideas how to combine quantum theory with relativity is still investigated as an alternative approach to String Theory.