Yea for Zappa! I'm also a big fan of John Hiatt's work. Johnny Cash, for sure. Though I don't listen to him much, Kris Kristoferson is widely respected. Love Nick Lowe, but he has not really stretched beyond his era of popularity. I just don't get Leonard Cohen. Maybe the songs, but I can't listen to the guy. And then the Lord decided we needed Miles Davis to compare all other jazz musicians to. And finally, let's not forget the incredible Willie Dixon and Big Bill Broonzy. The number of tunes those two wrote that defined American music and are a foundation to everything out there today are unparalleled.