My friend told me he wanted to see http://en.wikipedia.org/wiki/Andrei_Sakharov on this list. I must say that I don't know the guy, but based on the Wikipedia article, he was a brilliant Soviet nuclear physicist behind few of the largest man-made explosions ever to happen, and somewhere around 1960's he turned to political activism regarding dangers posed by nuclear arms race. In the political climate of 1960 Soviet Union, that was a brave move, too, and the powers that be made him lose much because of that choice.