Well, since Mafia is obviously not very popular, how about a forum-based
Assasins game?
The rules are following:
1. The players who sign up in this thread become known as "Assassins". Each player must assassinate their target (who is another assassin) in the manner described below. Upon a successful assassination, the target's targets becomes the assassin's new target, and so on. The winners are the last two assassins still standing, who receive the title "True Noir". :3
2. For the purpose of assassination, each player receives three words: their target's name, the Warn Word, and the Kill Word. An assassination occurs in two steps: first, the assassin must post the Warn Word in a thread where their target posted recently. If the next post by the target does not quote the assassin's post (particularly, the Warn Word), indicating that the target spotted the potential threat, the assassin can post the Kill Word in the same thread to complete the assassination.
3. The target knows their own Warn Word but not their Kill Word.
4. Upon completing an assassination, the assassin is to contact me via PM and point me towards the three game-relevant posts so that I can confirm their success. Posts that have been retroactively edited in any way don't count.
5. Some time after a successful assassination, I will post the name of the target and the thread where they were murdered in this thread. After that, they are out of the game and their assassin receives the name and data of their target. Assassinations completed after one's own assassination, even when one's not aware that one's dead yet, don't count (sorry).
And that's it. I have a few more ideas but they will have to wait until I get some players.