Jack Kirby's Fourth World (Forever People #1-11, New Gods #1-11, Mister Miracle #1-18)
-Ahead of it's time, the books were all cancelled apparently because the stories were 'too complex' for readers and had a hard time finding an audience. Mister Miracle lasted a bit longer as he fit more of a traditional superhero mold.
Pick up New Gods 1984 #6 for the conclusion to New Gods.
The 1984 New Gods reprint series reprinted New Gods #1-11 in six issues (two per issue), and if you don't care about having them in the original eleven issues you can actually save money as they're the same price ($12 vs. $24 including #6).
Some trivia: the original Kirby run of New Gods is an 'unofficial' sequel to his run on Thor. The beginning of the issue starts with a mention of Ragnarok, which appears to be the same Ragnarok from Thor #128. And Thor's helmet appears in New Gods #5 as an Easter Egg.
He was originally going to do New Gods at Marvel but he wasn't going to have the freedom to do what he wanted, which included killing off all the Asgardians. So,
when he jumped ship to DC he brought the idea over with him.
More info
here.
Wonder Woman #291-293
-Featured Wonder Woman teaming up with all the major female heroes of the time. I remember enjoying it.
JLA #183-185
-One of my favorite JLA/JSA team-ups. Also features the revised New Gods teaming up with the two main groups to fight Darkseid.
JLA #200 and Batman #400
Two of the best Anniversary issues, IMO.
New Teen Titans #42-44, Annual #3
-The Judas Contract. However, I'd recommend starting with #1 as everything begins there really with the introductions of Slade, Grant and Terra over the course of the first three years.
Legion of Super-Heroes #290-294
-The Great Darkness Saga. Darkseid returns to stake claim on the civilized planets. If you like it, I'd recommend going back to #284 and continue from there. The Levitz run on Legion was on par with Titans and X-Men at the time.
All-Star Comics #58 and 59
-Introduces Power Girl, with her, Star-Spangled Kid and Earth-2 Robin forming a sort of 'unofficial' junior division of the JSA (a sort of precursor to both Infinity, Inc. and Young All-Stars). It was the first JSA story I ever read as my school library had a copy of the digest that reprinted it.
Green Lantern #76-87, 89
-The classic Dennis O'Neil/Neal Adams run. Interestingly, the series was cancelled at #89, most likely because it also was too complex for readers and dealt with heavy topics (for its time). The duo then moved over to Flash as back-ups in #217-219, however those issues aren't available individually.
Instead, you could get the digital trade collection, 'Green Lantern/Green Arrow', which includes all the GL issues as well as the Flash back-ups.
Saga of the Swamp Thing #20-50, Annual #2
-The Alan Moore Swamp Thing was (and still is, IMO) one of the best revivals of characters in comics. And it was such a simple thing really, by changing him from a mutated man with plant-based powers to a mutated plant that thought it was a man with plant-based powers. His run continued into the Modern Age, up to #64. I included the issues up to #50 because the American Gothic storyline that started with #37 (Constantine's first appearance) reaches an epic conclusion that involves Zatanna, Dr. Fate, Demon, Spectre, Phantom Stranger, Deadman and others and gives a major turning point in Zatanna's history.
However, I do recommend reading up to #64 if you find you like it.
Aside from the American Gothic storyline, some of my favorite issues were a few of the one-off issues: #28, 32 and 56.
The American Gothic storyline, itself, was a bit controversial. It was composed mostly of Swamp Thing trekking across America and facing various horrors that were cropping up due to the event. And one vignette, the one with the werewolf, got him a lot of flak.
However, it was interesting to see him explore the different areas of horror and even take on a fictional version of the
Winchester Mystery House in one issue.