This thread is dedicated to discussing variations on the Phalla / Wangshire / Mafia forum games. I'm going to start with basic rules and common variations / house rules, then add my own discussion in a separate post. As things come up in the thread that properly belong in this post, I'll edit it.
The Basic Rules
For a more in-depth discussion, see http://en.wikipedia.org/wiki/Mafia_Game
The "village" consists of all players in the game. Included in the village is a small number of bad guys. Normally, the bad guys all know one another at the beginning of the game, but nobody else knows anything about anyone other than themselves.
Each day (normally 24-hour period) the village discusses and publically votes for one person to be executed that night. At the same time, the bad guys choose one person to kill each night and PM the name to the narrator.
The good side wins if all of the bad guys die. The bad side wins if the number of good guys is less than or equal to the number of bad guys (on the assumption that at that point, they control the vote plus get their kill, so it's inevitable).
Usually, there will be one or more "special" roles among the good guys (and occasionally among the bad guys). Exactly who holds each role is only known to that person, although how many of each role exist is most often known.
Each night, the narrator gives the details of who died, and normally whether they were a bad guy. Some games also include clues or outright statements if someone who died is a good special.
Standard Special Roles
Roles will have different names depending on the theme of the game. Listed below are the usual "generic" terms for each role. Normally, specials exercise their power by communicating with the narrator via PM.
-- once per night can "investigate" a particular person and find out from the narrator if they are a bad guy. Variations of seers may be able to determine a good special as well, although they may be unable to distinguish them from a bad guy.
-- once per night can kill a person of their choosing.
-- once per night can protect someone from any death other than execution by the village. Whether they can protect against multiple attacks on one person in the same night is up to the narrator.
-- a group of good guys, usually of similar size to the group of bad guys, who start the game knowing each other, and that they are all good.
Many larger games contain multiple groups of bad guys working at cross-purposes.
At least one game has included a council elected every other night who are able to overturn the popular vote. Normally, this shifts the execution to the person who got the second-most votes.
The typical size for a group of bad guys is 3, although an individual game may have more, particularly if there is only one group of bad guys in a larger game.
Common "House" Rules
You may not communicate regarding the game with someone who is dead, unless there is some specific mechanic in place to do so. In that case, communication normally goes through the narrator.
You may not use any anonymous method of communication to discuss the game. Forum-based PMs, external IMs, and e-mails are allowed as long as the person you are talking to knows who you are.
You may not use screencaps to "prove" anything to anyone.
Normally, everyone gets a "flavor" role in the game. Bad guys and good specials usually get a normal "villager" role in addition to their special role. This keeps people from using their initial PM to verify someone else's role. The two most common ways to do this are to (a) use the exact same message to everyone, or (b) give everyone a unique villager role.
OK, I think I got all of the basics. What am I missing? What variations have you seen? What did you like / dislike? How do you balance something like this?