There's a good Doctor Who (11th + Ponds)/Star Trek: TNG cross over that just finished. It was pretty good.

"The Last Zombie" is a good series I have in TPB.

Y the last man is a good series.
Pax Romana is a good one as well.

Watchman is a pretty interesting dark classic. Superman Red Son is also pretty good

WE3, Black Hole, League of Extraordinary Gentlemen, V for Vendetta, All-Star Superman, Asterios Polyp, The Filth, I Kill Giants, Kingdom Come, Batman: Year One, Persepolis, and, of course, Watchmen are all great comics that only last for one volume. There are a lot of great long-form serials, of course, but these are all great works to get yourself into the medium.

Neil Gaiman's Sandman is my favorite and Kevin Smith's Batman runs are really cool. If you like weirder stuff you could check out Johnen Vasquez's books: Johnny the Homicidal Maniac, Squee, and I Feel Sick.

The series "The Twisted Tales of Bruce Jones", and his graphic novel "Somerset Holmes"

"Soulless" by Gail Carriger (novelist) and REM (in process of adapting novels into manga)

Anything by Alan Moore (100X better than the movie adaptations of his work)