I agree with Sandman. Neil Gaiman is one of the best writers of all time. Alan Moore is brilliant. Of his, I think The Ballad of Halo Jones doesn't get mentioned as often as it should. It is fantastic. I really wish he'd settle things with the publisher so he can go and finish it.
The Walking Dead, Preacher, Invincible, Transmetropolitan, and Gravel are my favorite series. As for graphic novels, anything and everything by Warren Ellis or Garth Ennis, The Crow, 30 Days of Night, and Top 10.