I'm working on a game set during the Great Depression... in Space. You play down-and out hobos tramping between the solar system's planets and moons, joining hobo jungles on deserted relay stations and trying to survive.
The game is about trust and betrayal, and so the system makes use of Prisoner's Dilemma mechanics, using Companion and Accuser to represent the two choices in the traditional dilemma.
Characters have four ratings: one for each of the four outcomes in the PD, and these are dice pools. So you allocate dice during character creation to your Cooperator, Suckerpuncher, Martyr, and Fighter ratings.
During conflict resolution, players first slap down a single playing card: red for Companion, and black for Accuser. If both choose companion, each player gets three dice to add to their Cooperator dice for the roll, and have the opportunity to earn experience points. If both choose Accuser, they each get one die to add to their Fighter dice for the roll. If one chooses Accuser and the other companion, the Accuser gets five dice to add to the Suckerpuncher dice, and the Companion must roll straight Martyr dice.
In addition to these base ratings and the outcome of the card play, players may have "props" which allow one die each in a given circumstance. So a character's bible may be useful when the struggle is one of words and rhetoric, and a character's pistol may only add a die in shootout situations.
In addition, I'm working out a system of TSOY-like Keys. The idea is that cooperation is the only way to get XP for everyone, and it's how you get ahead rather than simply survive or win the roll. But there may be keys like "What does not kill me only makes me stronger" that gives you XP when you fail a Martyr roll, or "I'll get you next time!" when you fail a Fighter roll. Another idea I had was "Born Leader" that rewards you for getting five successive C/C or A/A pairs in a row (no suckerpunching for five draws) or "There's a sucker born every minute" for successfully Suckerpunching five times in a row (and folks know that you have this key, and won't trust you, so you'll have to convince them!)
My current chargen plan is that each hobo character has ten dice to allocate: each of the four ratings must be at minimum one and at maximum four, and a maximum of three props and two keys may be purchased at one die each. I'm thinking that experience points are five to a die.
Since this game uses dice pools, there will be basic minimum difficulty ratings even for contested actions. So two fighters using only their one die from the card draw will never be able to best each other, because the base difficulty would be, say, 8. So both sides would parry for a while and then fall back in stalemate.
Obviously my two strongest influences here are risus and TSOY, but I'm still kneading this one. I plan to work in rules about winos (to bring in the third ingredient from the second step) or perhaps use "invincible" for contests with forces so great that the stakes rely entirely on the Prisoner's Dilemma card draw, with no dice to follow.
I'm keeping a working copy of this stuff up at if folks want to keep track of my progress when I'm not posting in here.
I'm wide open for comments and criticism. I hope to round this stuff off tonight so I can begin playtesting.