My answer is hands down Josh Ritter. I'm a sucker for well-written, meaningful lyrics and this guy is easily one of the best in the business. He puts on a hell of a live show too. How about the rest of the GB community?
Clutch. I don't get how they're not totally huge as they have been around for for over 20 years and have a giant following but somehow they've never really broke through to that really huge audience. The closest thing they've had to a "hit" is their track "Electric Worry" which some of you may recognize from the Left 4 Dead 2 ads a few years back, though it's not terribly representative of their style which has varied quite a bit throughout their career. They've also had their songs appear on TV shows like The Walking Dead and Sons of Anarchy, Here's a few tracks from throughout their career but believe me when I say that these barely scratch the surface.
Just recently discovered Baroness via the Twitter feed of David Goldfarb, the executive producer for BF3's SP campaign. I love the instrumental stuff they do, the 'singing' bits are an aquired taste, but I do warm to their peculiar interplay somewhat. T'is my favorite song of theirs thus far. Every now and then I delve into their more aggressive materials. Outstanding muscians, and a very 'genre' singer. Unique, and awesome.
The messages and ideals behind their songs resonates with me well, especially songs like System... ...Meltdown and Stalemate.
Most people I show them to hate them though as they say they're too dubsteppy or too hardcore. I love them because of the balance of both genres.
Big Black. Although they were pretty influential on future punk, noise and industrial bands, a lot of people have never heard of them.
Also, there's this French post/black metal shoegaze-y group called Alcest, and their sound is both unique and beautiful. More people need to know about them.
David Johansen from the New York Dolls is pretty good, and they don't really get much credit for their recent work and some of his solo stuff;
Always enjoyed the music of Johnny Flynn, he seemed to miss out on the neo-folk revival (maybe to his benefit considering it includes acts like laura marling / mumford and sons)
And Death, its insane to think this was from 1974
Slug from Atmosphere is one of my all-time favorite lyricists. It's rare when a rapper can kick ass in a freestyle battle and then sit down and write intricate rhymes rich with symbolism and storytelling. It's never pretentious, though, which is what makes the music so perfect to me.