Hey, I know a lot of people have suggested lawyer (since mob lawyer is a very realistic, natural thing), but most have suggested that they do something subversive at night to hide the mafia, when they should really be acting during the day. I'm a total nub to the forums, I know, but it doesn't take an expert to realize that the mayor can't make much of a difference until the end game. If a mob lawyer were the mafia alternate to the mayor, giving x number of votes (but not saying WHO was giving the extra votes), the mafia would only need to convince a few townspeople into voting innocent (still difficult) in the face of a lynch to save the mob on trial. At that point, the mayor role would have serious purpose, allowing him to counteract the lawyer votes. Also, to make this interaction seem a little more intentional, the mayor role might have its name changed to "District Attorney" or "Judge" or something of that nature.
Here's an example of what it would look like:
New Role: Lawyer
Affiliation: Mafia
Summary: A corrupt lawyer who manipulate the courts in favor of the mafia
Goal: Mafia wins.
Power: During the daytime, you may type -vote to give you X extra votes for a day. The town will be alerted that a lawyer is influencing the vote (or not, depending on setup), but your identity will not be revealed.
Investigation:
Sheriff: Mafia member
Investigator: Your target is a leader among men
EDIT: Less than 5 minutes after posting and I already forsee a problem with this. Nothing is there to stop the lawyer from waiting until the last second to type -vote so that the mayor has no time to react.