Signature started as my "Ultimate RPG." While making it, I had a breakthrough in terms of mechanics.
The result? One simple, fast mechanic for character generation, action resolution, setting control, and story control, that handles any level of power, and any level of detail. The designer can customize by setting which behaviors are rewarded, and which are penalized. There is also a generic "power" mechanic called Resources, which reflects all the various kinds of special powers in a given setting.