I just finished the Walking Dead myself, and I have to say it was amazing can't wait for Vol 10 to come out.
I bought a bunch of Garth Ennis' Punisher series and I have to say that it is good aswell, really gritty and realistic, pick up a vol and I guarantee you will be hooked.
Also grabbed vol 1 of The Boys, i'm hooked going to pick up vol 2 and 3 at the end of the week.
Ed Brubaker had an old series at WildStorm called Sleeper that is amazing, which had a followup called Point Blank. It has a few superhero types in it, but isn't a superhero book by any reach.
I seen someone mention Powers, It has Superheros but in a wierd way, Bendis is an amazing writer I suggest picking up a volume. Bendis is the best writer in comics in my opinion.
And I might get harped on for this but I'm going to say WildC.a.t.s 3.0 Which is hard to grab since it all wasn't collected but an amazing series.