I honestly have no idea - I’m not sure I’m well versed enough in the history of roleplaying game mechanics to be qualified to even say what revolutionary is. Instead, I guess I will talk about a few mechanics I’ve found particularly interesting.
The whole concept of aspects and the fate point economy in Fate really blew my mind and excited me about the possibilities of more narrative-focused play. I’ve never yet had the chance to play a Fate game properly though so it will have to remain theoretically interesting rather than practically.
Another game from Evil Hat showed me some mechanics I really enjoyed - Don’t Rest Your Head. DRYH uses a cool system where dice pools are made dominants based on the highest rolls within them (rolling low is for successes) and the dominance of a pool effects the flavour of the narrative outcome (madness, exhaustion, pain, discipline), regardless of whether or not the roll was a success for the player or not. Again, another narrative-focused mechanic, one that I find super interesting and this time one that I’ve had the pleasure of experiencing first hand, having both played and run DRYH.