William F. Buckley
UPDATE: Well, there's this.
Update 2: just to clarify (and preempt some flaming) - I'm not much of a NR guy, and Buckley's brand of conservatism wasn't as pro-liberty as I'd like -- indeed, sometimes downright anti-liberty -- but his providing an intellectual and popular voice for conservatism made the left less complacent and, even if it wasn't his intention, helped open the door for libertarian voices to jump in to the fray. (Was that too many mixed metaphors? Sorry.)