Ok, so I had this idea for a mechanic. You know how in Settlers of Catan you have 5 basic things you can build? Well, what if those building costs were asymmetric? Or even the things you can build were asymmetric? Or what if there were tiles with additional stuff you could build or do, and those tiles could be purchased? So I could on one turn buy the tile that would allow me to construct different things for the rest of the game, (like trebuchets or moats or something, I don't know), and only I could build those things, and there would be a lot of different tiles. So each game would be vastly different because you could get different tiles allowing you to build different structures which could change your strategy completely.
If anyone is reading this, feel free to steal this idea.
Another idea I had while in Walmart earlier today. I saw a self-contained little Risk card game thing, here let me just find a picture...
Anyway, those are my two game mechanic ideas I've been thinking about.