Some weird idea I had a while ago. It's not all that greatly executed, but anyhow, the weekly design contest made me think of this.
Introducing "Feats", a mechanic inspired by RPG skill trees. Basically, if you do certain things during the game, put a coin token on the spot of your "Feats" mat (each player gets their own). My current design has the Feats be dependent on each other, starting in the bottom row - so like in a real skill tree, you can't get the one for gaining a Province without either drawing your deck or gaining a Duchy first... Etc. Of course there would be cards that care about the Feats you achieved. Just some examples... This is really experimental, so don't expect great things. That goes for both the actual cards as well as the conditions themselves.
Also, if you misread "Feats" for "Feast", that's totally your fault, not mine
There is no Feast Feat.
Edit: Changed the card type from "Courage" to "Fame". Another one that sounds familiar. No, not THAT Familiar!