Swamp Thing #37Written by Alan Moore
Penciled by Rick Veitch
Reason:
The first appearance of John Constantine. Constantine would go on to star in his own series, Hellblazer, beginning in 1989. Hellblazer is the only Vertigo title that has been in print continuously since the imprints inception.
Animal Man #26Written by Grant Morrison
Art by Truog & Framer
Reason:
In this final Morrison-penned issue of Animal Man, the story that Morrison is now renowned for comes to it's weird finale, with Morrison interacting with the title character. Breaking the 4th wall in comics at its most bizarre.
Swamp Thing #21Written by Alan Moore
Pencilled by Stephen R. Bissette
Reason:
This was only Alan Moore's 2nd issue, but he went ahead and made some sweeping changes to the character, which set up his now-epic run on the title. Namely, (spoilers--highlight to reveal)that Swamp Thing was not Dr. Alec Holland, transformed by a chemical explosion, but rather a plant elemental formed from swamp goo transformed by the chemical explosion that killed Holland (/spoiler).
Doom Patrol #19
Written by Grant Morrison
Pencilled by Richard Case
Reason:
Grant Morrison's first issue on Doom Patrol started another landmark run. More significantly, rarely has a creator made such drastic changes to a title with his first issue on it, but Morrison went to town.
Watchmen #12Written by Alan Moore
Pencilled by Dave Gibbons
Reason:
Well, it's Watchmen, the best comic book ever, so it's kind of a given that it's going to appear somewhere on any list of most important comics. Issue 12 was the finale of the maxi-series, and helped set the precedent for 12 issues being the standard maxi-series length.
Sandman #8Written by Neil Gaiman
Art by Dringenberg & Jones
Reason:
The first appearance of Sandman's sister, Death, and, by extension, the Endless, which go on to play a major part in the Sandman series. Plus, the story, "The Sound of Her Wings," is really good, too.
See the full list, plus explanations for all of 'em, here.
