HL Mencken
Existentialist Cowboy has a post about the great HL Mencken, perhaps our nation’s greatest satirist since Mark Twain. EC notes that “Iconoclasts are always misunderstood; truth telling has become un-patriotic. Were he alive and writing today, Mencken would be assailed for telling the truth.”
Thomas Frank is perhaps the closest thing we have to a Mencken today, but he's not nearly prolific enough.
(Thanks to Mike at Crooks and Liars for the tip.)