8. Mr. Fun
Mr. Who? Yes, Mr. Fun. The character first appeared during the 2002-2003 arc, "Family". He's a mild-mannered family man, but is also a deadly hitman who's been under the employ of several mobsters, and members of Batman's Rogues Gallery. Yes he uses a golf club, but don't let that fool you... He's kind of like "Mr. Brooks" meets "Stepdad" and has no problems taking out anybody that gets in his way. Seeing this guy on the series doesn't take much imagination. A hitman on the run from the GPD? He could potentially be the Gotham answer to Arrow's, Deadshot.
Ideal Casting: Needs to be somebody who can be seen as an everyday man. Preferably somebody that can pull off some altering dark & light humour. If they went with an aged man, I'd like to see someone like Kelsey Grammar or Christopher Lloyd. If they use him and they go for a younger guy to portray him? Seth McFarlane. Can't you just picture him in business-casual attire, beating somebody to death with a golf club? If you can't, that probably means he'd be perfect for the gig.