What interesting mechanics exist out there?
I don’t mean just “here’s a new way to roll combinations of polyhedral dice”, or “here’s a new theme overlaid on a standard progress tracker”, or “here’s stress with another name”.
I mean, actual new conceptual mechanics that produce new and interesting behaviours in-game. Things like CoC’s push rolls, or Slugblaster’s Beats/Character Arc, or Blades in the Dark’s Flashbacks (these might not be the first games that those appeared in, but the point isn’t the game, it’s the mechanic).
Interested particularly in what those new mechanics bring to the table in terms of player interactions or story development.
Dune: Adventures in the Imperium does a version of this. Extra successes on a challenge give the players Momentum points which they can use to generally make things better for them. But the GM has Threat points which make things harder for the players. Points can also be used to buy off bad outcomes or improve good ones.
But the most fun bit is that the GM can cash in a bunch of Threat to introduce a rival to the players into a scene. So their nemesis can drop in on the party where they’re trying to gather allies to confront the nemesis.