Don't know if somebody else has claimed it, but I'd like to try a Warhammer 40K Mafia. I know I need to get a few games under my belt (haven't gotten to play one yet!) but the 40K universe sounds like it could be easily ported to mafia.
EX: Two mafia families= Inquisitor (Cop, can investigate or kill at night, not both), Space Marine (kill only) and Imperial Guardsman (kill only) vs Daemon (can infect psykers, making a psyker townie a member of the mafia), Chaos Marine (kill), and Mutated Heretic (kill). Throw in a Medicae (doctor), a Dark Eldar Pirate (Serial Killer), a few psykers (vague investigate with a failure chance, also chance of burnout (death) when attempting to investigate), and of course, the vanilla townie.
So... what'cha think?