Here are some that I would suggest.
Fables: Basically it's places classic fairytale characters in the modern world. That's a very simplistic description. It is a great series.
Y the Last Man: All the guys in the world have been killed by a virus except for one guy.
Read the first issue free.
DMZ: America is caught up in another civil war and Manhattan is a demilitarized zone. A photo-journalist sent to cover the story gets caught in the DMZ.
The Watchman is good. Much better than the movie.
Bone: It's a little more all-ages but still really good. Think Looney Toons meets Lord of the Rings.
Invincible: It's a cross between Spiderman and Superman but set in its own world.
Read the first issue free.
If you're looking for Batman graphic novels I would suggest
The Long Halloween and
Dark Victory. The Dark Knight Returns, The Dark Knight Strikes Back and Year One are all good too.
For those of you who haven't yet, you can read the first issue of Walking Dead online.