For whatever reason this morning as I was waking up, my mind starting to think of comics that really utilize the idea of space and time on the comic page. I only have three examples here, and in the case of Alan Moore wanting to restrict it to one example, and hope someone out there reading can come up with some more ideas.
Robert Crumb's SHORT HISTORY OF AMERICA; I guess my first exposure to this sequence was the still frames in Terry Zwigoff's CRUMB documentary.
Alan Moore/Mike White's THE REVERSIBLE MAN from a 2000AD Time Twister; as Moore quickly abandoned drawing his own stories quickly, it isn't surprising that the real experimentation isn't with the actual comic book page, but the storytelling. This notion of malleable time pops up a lot in Moore's comics (in particular the final fate sequence of William Gull in FROM HELL with Eddie Campbell, throughout PROMETHEA with J.H. Williams).
Richard McGuire's HERE; This short story I was so amazed at, I photocopied it and showed it around to people when I really wanted to show how awesome comics could be. Some guys did a student film doing a live action adaptation of the story, which would seem obvious, and fails not just because of production value (I'm sure David Fincher could do something very seductive with it), but something is lost when you lose the nature of the comic page.