I had a thought for a suggestion game that I think could only be reasonably ran by freeformschooler (or at least his is the only excessively convoluted game I've seen on these boards.) However, I'm fairly befuddled today, so this is going to be pretty rambly at best, and nondescript at worst. Actually, the main premise can be summed up in a couple of words. Time shenanigans. "Players" would have "hammer-time," by which I mean to vaguely reference "hammer-space." If anyone doesn't know what hammerspace is, it's an infinite extradimensional space always within reach that you can always draw exactly what you need from. What I mean by hammer-time, besides the eventual pun, is that players would be able to select any point in the story that they've already passed and change any number of things in that scene (within the capabilities of the Player Character), and then the game master would update the "current" situation to reflect all the permutations resulting from that one change. As an example, if the "players" were in a temple with a glowing green gem in a statue in the middle of the room, too high up to reach, and they ignored it to explore the temple, finding a secret passage underground with a sphinx that required the temple's gem, they can retcon the first scene so that they piled benches high enough to reach the gem and had always had the gem with them.
Huh. Come to think of it, the effect might be better referenced as retcon. I prefer hammer-time, at least for that pun, and retconning seems more like something at the GM's disposal rather than the "players'."