I never knew Samuel Edward Konkin III in person, and knew of him only through his moderation of the LeftLibertarian mailing list. But he seems to have made quite an impression on the modern libertarian "movement". This interview captures the flavor of his thinking (see also his essay on copyright). He's best known for The New Libertarian Manifesto, which presents an "agorist" approach to politics and society (from the open marketplace of the Greek agora) that eschews party politics and working through the system. I must say I still doubt the realism of his analysis in many respects, since his faith in the withering away of the state seems just as misplaced as that voiced by the Marxists. But it makes for provocative reading nonetheless.