GMless RPGs?
Mythic is one I've heard of. It is designed to be used in conjunction with a GM emulator to create random adventures for the party to go through.
On a website I found this as an answer to your question:
Universalis gives everyone pennies to "pay" to make a thing true. The points replenish by doing things the system wants to encourage, such as getting involved in conflicts, win and lose. This basic dynamic can be adapted in a variety of ways.
Fiasco has a fixed number of dice available to roll. They serve as a pacing mechanic, with the story twist happening when they're half used, and when they're all used the game session ends.
Polaris splits GM authority among all the other players when a player's character is in the spotlight. The player opposite is responsible for presenting conflicts tailored to the spotlight player, while the rest are responsible for the impartial referee role, and for throwing in suggestions when the opposition and spotlight players need ideas.
Archipelago II (which is free to download) dispenses with dice and uses ritual phrases (similarly but differently to Polaris) to trigger twists or alterations in another player's narration. These phrases have "soft" effects that require a response from the narrating player, but don't force them to narrate something particular, so that they retain full authority over the story they're telling about their character. Ritual phrases are fixed words to speak and have defined effects: things like calling for more detail about something, asking for the player to narrate an unspecified obstacle and how they overcome it, or asking them to narrate in a different direction.
In addition some games like Wraith the Oblivion had some semi-split GMing duties because each player at the table also played the "demon inside" another character. You could expand that outward to having players as the "demon" take greater ST responsibilities.
