If you've never heard of Fiasco, there's plenty of reviews out there that will tell you the basics. I suggest taking a look at:Rather than cover all that ground, I'm just going to mention a couple things I particularly liked, and a few I didn't.
What I loved about the system:
- The charts and mechanism for creating character relationships were awesome. There was a random element, but the players had a collaborative decision-making process to go through in choosing which (rolled) numbers to use on which charts, and interpreting those chart results. It was great source of inspiration, and made sure everyone had a voice in how things started. I will absolutely steal this idea for future one-shots I run that may or may not use any other mechanics from Fiasco.
- The "Tilt" mid-game. It uses a similar mechanism to the character-creation system to show us the end goal/condition half-way through the session. This was pretty genius, and helped us provide structure at the point where the game was just about to explode out of control.
- The "Aftermath". Not quite as cool as the character creation and tilt, but still pretty neat. Each PC got a montage of images showing the impact of the events detailed in their future life.
- The unstructured GM-less mechanics of the scenes themselves. The set-up, tilt, and conclusion mechanisms were all pretty awesome, but I wasn't completely enamored with what went between them.
It felt a little too "Gong Show" or "Voted off the Island" for me. The other players voted on whether the scene was beneficial or damaging to your character, which in and of itself was just an okay mechanic. Problem was there wasn't a clearly-defined end point for a scene, so you didn't know when to start kibbutzing about the voting part. If someone jumped the gun, it would disrupt the scene / spoil the moment.
I could easily imagine situations where it would lead to out-of-character social tension as well, like Player A constantly cut Player B's scenes short, always gave Player B a damaging vote, or metagamed the voting procedure to make sure the Aftermath for Player B was dismal. With some groups I've gamed with in the past, that would have been a recipe for disaster.
- Giving away your results dice in the first Act. My dislike for this may have had to do with the impromptu nature of our session (we'd all showed up for a different game, but there'd been too many players, so some of us broke off into a second table, and decided to play Fiasco instead). Since we weren't prepared for it, the description of how things worked was a little weird, and I couldn't quite internalize what the giving away of the results die represented... if indeed it represented anything. It may have been purely mechanical. The second Act, where you keep the results die for yourself, made more sense to me. The first act felt more like a board game too me, where the mechanics trump the story, and the second felt more like an RPG where the mechanics support and enable the story. I can't say for certain how much of that had to do with this one little rule change between the two acts, and how much had to do with simply progressing through the games learning curve (which is very light, but not transparent).
- It was over too soon. I expect a 5 or 6 player game is probably about the right length, but the 2-act structure seems to make a 3 or 4 player game just whip right by. It was over before we knew it. I'd like to add a third Act for smaller groups, but I imagine some changes would have to be made to the Tilt and Aftermath to make that work.
Final note: I'm not 100% certain that it needs to be GM-less, and I think it might actually work better if there was a single authority giving it structure during the bits that aren't chart based. You could then just essentially use the Tilt and Aftermath as an improv tool for the GM.