So far on Fox's Gotham, we have Penguin, Riddler, Catwoman and Poison Ivy. Not to mention famous crime bosses Carmine Falcone and Sal Maroni. Producers have promised that Victor Zsasz and Harvey "Two-Face" Dent are on the way in future episodes.
Now we have confirmation that another baddie is coming to Gotham City, though probably not yet in his villain identity.
Hush, a.k.a. Tommy Elliot, will be seen on a future episode of Gotham. Since Tommy and Bruce Wayne were close friends when they were boys, it makes sense that this future super villain would be seen at this point in Gotham's storyline. Don't get your hopes up too high for a big Hush storyline, though. Actor Sean Pertwee, who plays Alfred Pennyworth, told IGN that Tommy Elliot will only appear in easter egg form for now.