Ongoing or limited series, graphic novels, TPB's, strips... I don't discriminate.
  1. Calvin & Hobbes by Bill Watterson
    By the gorgeous box set and read it constantly.
  2. Watchmen by Alan Moore
    Read the articles too.
  3. X-Men: The Dark Phoenix Saga by Chris Claremont
    Best X-Men story period.
  4. Alias by Brian Michael Bendis
  5. Peanuts by Charles Schulz
    1963-1964 are my personal favorites.
  6. Bone by Jeff Smith
    Personally I like the One Volume Edition in B&W
  7. Batman: The Killing Joke by Alan Moore
    Haunting in both subject matter and efficiency of story.
  8. Y: The Last Man by Brian K. Vaughan
    My favorite arc is Vol. 4 "Safeword" but the whole series is great from start to satisfying finish.
  9. Captain America: The Winter Soldier by Ed Brubaker
  10. Laika by Nick Abadzis
    Based on a true story.
  11. Identity Crisis by Brad Meltzer
    A superhero whodunnit!
  12. Astro City by Kurt Busiek
    Best issues are vol 1 #2, #1/2, and the "Tarnished Angel" story arc.
  13. Usagi Yojimbo by Stan Sakai
    You can jump into this at any time. No need to read from the beginning.
  14. Batman: The Dark Knight Returns by Frank Miller
    Read it again.
  15. We3 by Grant Morrison
    Utterly tragic.
  16. Sex Criminals by Matt Fraction
    Not what you think it's going to be.
  17. I Killed Adolf Hitler by Jason
    You want to read everything by Jason after reading this.
  18. Preacher by Garth Ennis
    It gets weirder.
  19. Mouse Guard: Fall 1152 by David Petersen
    Most bad-ass mice since Jonathan Frisby.
  20. Marvels by Kurt Busiek
    Major superhero events from the spectator POV.