Some ideas:
Reverse Traitor: In the Mafia, but wins with the Town. Can't think of a fair mechanism for the Mafia to find out/eliminate them.
Insane Cop: Always returns reversed results, no knowledge.
Daycop: Same as Cop, but posts in public and recieves answer during the same day by PM (e.g. "Investigate: Soleron". Anyone can still fake "Investigate:".
Inventor (one Town, one Mafia?): Can come up with one Invention name. Mod invents role based on that name.
Necromancer: Brings back a player from the dead once
- Person who must roleclaim something on a specific day
Nemesis: Person who must vote a particular person every day. This can be faked and claimed too, so not as obvious as you think.
Role Investigator
- Power to swap two person's roles and alignment
Poisoner: Chooses a target each day, that person is informed publicly they have 2 days to live (rather than dying instantly)