My all-time favorite is Yuengling, hands down. Not only for the beer, but because it's an American, family owned brewery, and it's been around for so long.
While I have only had home brewed cloned versions of their beer, I would vote for Surly Brewery for an American craft brewery. I would love to be able to go to a local store and buy a six pack of Surly Cynic. What I brew is fantastic. The NB kit. I wonder how close I am. Theirs is probably much better, but I can't brew this fast enough.... neighbors, friends, me, etc...