I'll second everything Ignatz just listed. My own comments:
- Palomar and Locas are part of Los Bros Hernados' long running series Love and Rockets; while I haven't read the big Fantagraphics re-issues, I've gone through about 1/3 of the original L&R run and really dug them. I personally lean towards the Locas material, but it's all excellent.
- Maus won the Pulitzer Prize, which should tell you that it's no ordinary comic. It's an astounding account of both the Holocaust and Spiegelman's relationship with his father. Crucial reading.
- Watchmen is the final word on superheroes. V for Vendetta is a close second. Alan Moore is a pagan god who manifests as a snake puppet that I worship. Well, not quite, but his comics are incredible.
- Preacher is what you would get if a hard drinking John Milton decided to write the rockabilly bastard offpsring of Paradise Lost. "Good like Sandman but completely different" is absolutely right.
Also, here's a few recommendations of my own:
The Frank Book by Jim Woodring - Surreal, haunting dream imagery like you've never seen before. There really isn't anything else quite like Jim Woodring's mad visions. There's no dialogue, so you're here for the lush, somewhat disturbing art, not anything like plot or characterization. The Frank Book is a bit pricey, but it collects all of Frank's adventures and is suitable for refined, mischevous coffee tables everywhere. At least make a point of flipping through it at your local bookstore or comic shop.
Persepolis by Marjane Satrapi - I generally don't go in for autobiographical comics, but I definately make an exception for this account of life during the Iranian Revolution. In the first volume, Satrapi becomes a teenager as the revolution takes hold. Beforehand she and her parents are liberal and politically active; afterwards, they're trying to survive and fighting small battles, including a hysterical anecdote involving Kim Wilde's song "Kids in America". In the second volume, Satrapi has been sent abroad for high school; she returns after the Iran-Iraq war to see her country rebuilding, yet still oppressed. This is brilliant, gripping stuff, even when she's discussing teen angst and hippie comunes. Your local library is likely to have a copy.
Transmetropolitan by Warren Ellis and Darick Robertson, et al - The near-future saga of Spider Jeruselum, a cyberpunk Hunter S. Thompson, and his gonzo battle against political corruption. Ellis wallows in black comedy, satire, SF worldbuilding, and characters who specialize in swearing, chain-smoking, and mayhem; Robertson illustrates all this with gleeful detail. The combination is guaranteed to knock you on yer ass. Like the other two Vertigo stalwarts Sandman and Preacher, Transmetropolitan knows when to quit and is nicely self-contained at 60 issues, all of which are in print as graphic novels. Note that the pic above isn't the first volume; you'll want to start with
Back On The Street, which collects the first three issues, cheap, and sets up the series; however, I should note that things really start to pick up with the second volume, Lust For Life.
FnordChan