Round-Robin Gaming

The System: your choice (3.5 for tonight)
Players: 3 - 5 each must be able to GM
The Game:
     The precipice for this game is that each individual will take turns GMing. You should determine before hand what will break up the micro-sessions. The only thing that the GM controls is the area that is immediately relevant to the players, this allows the next GM to change the landscape without contradicting the previous GMs.
     Since each GM is also a player character they should still be factored into the party during their turn GMing, however for the enjoyment of the other players they should temporarily take a background or supporting roll. Introducing new NPC characters and determining the current objective is up to each individual GM on their turn, and does not need to directly correlate to any previous turns, however a good GM should be able to bring everything together in a unique and interesting way.
     In order to keep things even more interesting, each GM/Player is given one GM token to use to change something about the current situation as only a GM could. The token's reset with each new GM. This ability should not be used to boost one particular character, however saving someone, or altering the environment are perfect uses.
     In order to make this a feasible situation, our group commonly either makes the players explore a previously unexplored island, or a new material plane, or anything that has an exceptional ability to be changed on a whim. For instance having the party running through only one particular dungeon the entire time would be incredibly limiting to GM's and would limit the creativity that this type of play is meant to encourage.