I just read Robert Nozick's Anarchy, State and Utopia for the first time for a seminar on liberal democracy, and while I'm a non-libertarian who disagrees with most of his positive arguments, it's brilliant. Nozick was also a wonderful writer (a special delight after slogging through John Rawls' A Theory of Justice), and the combination of his intellectual and rhetorical genius is absolutely devastating when he's taking on cant and bad arguments. Given my Spinsanity background, I can't help but love it.
Reading Nozick also reminded me of a hilarious New Republic article from the 1980s documenting how this passionate libertarian extorted more than $30,000 from his landlord by exploiting rent control laws of the sort that he decries philosophically. It doesn't undermine the strength of his arguments, but it certainly casts him in a much poorer light. Check it out.