Pretend you are going to moderate a Mafia game. You have 20 players to work with. What roles would you use?
The idea for this is to come up with a set-up where all the roles fit together nicely; none too powerful or too strange. Provide any back-story you want, etc. I won't say no themes allowed, but for now, it would make more sense to stick to a normalish game.
You can post your ideas in this thread, or PM them to me, and I'll post them all together in a few days (you can choose whether you want it to be anonymous or not); then everyone can provide positive feedback and such.
Not really sure how successful this will be, but we can always switch topics if this one sucks.