Here are a couple of mine:

(1) Marvel's New Universe. Back in the 1980's, Marvel decided to create a new line of comics devoted to a new universe with new characters. It was a modern day realistic Earth where all of the characters were powered up by a mysterious "White Event". At least, they were supposed to be. Some writers didn't get the memo, so you also had things like an extra-dimensional vigilante (who had to be retconned later) and a guy given his powers by a mysterious alien (which also had to be retconned).

The fascinating part to me was the comic D.P.7, in which many of the characters were still figuring out their powers, not knowing exactly how they worked or what exactly they could do. So, I made a game with a mysterious "Black Event", after which the PCs got powers. The players only got to make the non-powered version of their characters. They had no idea what their powers would be except that they were told that the more useful their non-powered character was, the less useful their powers would be (and vice-versa). And the PCs had to slowly figure out their powers. One guy had mastery of the electromagnetic spectrum (but really only knew he could do stuff with light), one guy could time travel but only to a point in time and space where one of his ancestors lived (and he only ended up doing so by accident when in danger), and one guy had phenomenal power over matter, capable of telekinesis and, to a lesser extent, transmutation.

(2) Jack Chalker's Midnight at the Well of Souls and to a lesser extent DC's Green Lantern: Mosaic and maybe a bit of Marvel's 1980's Secret Wars.

Those inspired me to create a game in which there was a "mosaic" world, created from pieces of other worlds. In each piece, the rules of reality were completely different. In one area, high technology worked, but not magic. In another, magic worked but not technology. Another area allowed special abilities only if you had sung about those abilities. And so forth. It wasn't so cut and dried though. In addition to generic fantasy and generic sci-fi, there were more specific settings: monster movie horror, fairy tales, Greco-Roman fantasy, martial arts competition, kids cartoons, and so forth.


There was a lot more to the game, but that was the setting.