So bros, here's a million dollar question:
Shall I post moar (there's still stuff to go through, Morrison has written a lot of JLA over the years), or shall I post his more highbrow (seeing how Codex hates on ADVENTURE) work? The work in question would be Doom Patrol, with finishing touch through its "sequel", Flex Mentallo.
Doom Patrol is one of typically accepted Three Great Works of Grant Morrison (being Animal Man, Doom Patrol and The Invisibles). In it he takes full control over writing an old C-List superhero team called Doom Patrol, which consists of freaks and outcasts. It's a glorious series of stories about metaphysics, metafiction, surrealism, psychology, rationality/irrationality, The Smiths discography, and (obviously, since it's GM) the human spirit. One of the central characters is Cliff Steele AKA Robotman, a former douchebag race driver who is reduced to being a brain enclosed inside a robotic body, and if you ask yours truly along with The Swamp Thing one of the most noble fictional characters of all time. The team along with him is Negative Man, a man who is bonded with the Negative Spirit Rebis (and world's first hermaphrodite superhero after GM gets to work); Crazy Jane, a woman with multiple personality disorder whose 64 different personalities all have different superpowers; Dorothy Spinner, an ape-faced girl whose imaginary friends are real; the team led by the wheelchair-bound genius doctor Niles Caulder.
Flex Mentallo is the indirect follow-up of Doom Patrol, a metafictional miniseries about superhero comics and the superhero concept. Grant Morrison's personal "superhero bible" some would say. The story happens on two levels, one is the story of a rockstar named Wally Sage (revealed in Supergods to be partly an "alternate life" version of GM himself), who is waiting for an overdose to kill him, calls a suicide hotline from an alleyway to talk about superheroes. All those shitty, amazing comics. The other is about a superhero he created when he was a child, Flex Mentallo, The Man of Muscle Mystery, on a journey as the world is ending. As usual, the story is Morrison's protest against the grimdarkening of superheroes and life in general.