Alan Moore, who did Watchmen, has done some other pretty amazing work. From Hell is a dark telling of the Jack the Ripper murders. V for Vendetta the comic is superior to the movie. The League of Extraordinary Gentlemen is far, far, far superior to the POS movie but I actually think it's the weaker of Moore's work. Transmetropolitan is a very fun comic. If you like Batman, which I don't really, look up The Long Halloween and The Dark Knight Returns. Hellboy and The Goon are both very fun--the latter is dark goofy funny in a sort of Sam and Max way, but even darker. Another worth mentioning is Maus, which is one of those things you never would have expected to be done in comic form. It's a biographical account of the author's father's experiences as a Holocaust/death camp survivor--it's really heavy stuff though you wouldn't expect it because everyone is drawn as a cartoon mouse.