The Maus series of graphic novels are wonderful.
In terms of the classics, I have a bit of a thing for Swamp Thing and the Hellblazer series. In fact, John Constantine's first ever appearance as a character was in an edition of Swamp Thing.
I find I am easily won over by James Jean's cover illustrations for Fables, and also the illustrations which were used for the covers of The Invisibles. They are really great.
But my favourite publication, in this genre, is Rogan Gosh, by Milligan and McCarthy. It's so abstract, with two stories running parallel to one-another throughout. It's illustrated and coloured in the style of Indian comic books, which is where the influence for it comes from, even though it's meant to be semi-autobiographical. It's pretty unique, and really exciting to simply look at - there is so much going on with each page! It's a bit of a treasure for me