4. Lock-Up
From the prolific to the not so prolific! Lock-Up - Real Name: Lyle Bolton- got his start on the popular Batman: The Animated Series, before he was picked up for comic duty in 1996. The character is a muscle-bound, disenfranchised, ex-security guard. He was Bruce Wayne's chief of staff, and he put a good word in for him at Arkham... where he terrified the s**t out of everybody, including Scarecrow. Subsequently he started to hunt, trap, and capture, baddies of Gotham City and dish out his own form of justice. He's been portrayed differently several times in the comics, but the one thing that remained was his M.O. It isn't hard to see how he can be worked in well with a series like Gotham. He doesn't even have to get his start the same, or be a security guard. He could be a disgruntled ex-cop, or private detective, or whatever they want him to be. It might not be a "Batman" series, but it doesn't mean they should skip over the vigilante angle.
Ideal Casting: Honestly, if the WWE could do without him, I'd give Randy Orton the part in a heart-beat if I were them. Orton's schedule not withstanding however? Michael C. Hall would do a good job at it.