The next Batman bad guy doesn't necessarily have to be bad, or a guy. The Huntress has clashed with Batman on a number of occasions, mostly because Batman doesn't approve of her methods. To borrow a phrase from every 70s cop movie, she's a loose cannon and she plays by her own set of rules. But before we get into it, some history. Back in the day, there were all sorts of different DC Comics worlds where Batman and Superman existed. In one of them, Batman got old, married Catwoman, and they had a kid, Helena Wayne, who grew up to be just like dad, but with a skimpier outfit and crossbows instead of batarangs. In the 80s, they ditched the multiple worlds concept, and since Bruce and Selina were too young to have a crimefighting daughter, The Huntress was re-imagined as Helena Bertinelli, the daughter of a Gotham crime lord who witnessed her parents' murders at the hands of rival gangsters. Like Batman, she grew up and decided to take on the Gotham mob, but unlike Batman, she was more interested in revenge than just cleaning up the streets. Hence the aforementioned clashing. Recently, the Huntress has hooked up with Barbara Gordon and joined the Birds of Prey, a great comic book series (especially under writer Gail Simone) which was turned into a terrible WB TV series in the early 2000s and quickly cancelled.
Pros: There aren't enough hot, slightly crazy in a good way, ass-kicking women in the movies. Plus, I think Helena Bertinelli is one of the more interesting characters Gotham City has to offer. And although I went with her more revealing costume for the header, she also has a more conservative one that the folks who freaked out over Black Canary Barbie can handle.
Cons: There's a whole lot of backstory to get through, which could make a Batman movie featuring the Huntress feel a lot more like a Huntress movie featuring Batman. And the association with the terrible TV series might scare off a studio from that idea. Plus my vague plot summary in the next section basically casts her as a sidekick in the end, and audiences would be confused about a non-Robin person at Batman's side.
How I'd do it: The generic Huntress/Batman conflict is her finding the guy who killed her parents and wanting to kill him, Batman intervenes because he doesn't believe in killing people, they fight, he wins, she gets pissed off and leaves. It's nothing fancy, and it would have to be structured around an actual villain, probably ending with them putting their differences aside and kicking the villain's ass, but it's a perfectly good story.
Casting Guesses: In the Catwoman writeup, I said I wasn't sure Megan Fox could act. In hindsight, she's not old enough to play Catwoman anyway. But she's physically perfect for The Huntress, the right age, and it's not as demanding a role as Catwoman. The Huntress is mostly just pissed off all the time. I can't even think of a second choice, to be honest, Megan Fox is it.
Verdict: Never gonna happen, the character carries too much baggage from the failed TV show and probably plays too much like a rebellious batgirl, but I think it would be awesome.
After The Scarecrow, Ra's Al Ghul, The Joker, and Two-Face, who should be Batman's next enemy in the Batman Begins/The Dark Knight series? Well, as of now we know that Tom Hardy will play Bane and Anne Hathaway will play Catwoman.
Check out the master list for all the villains covered. I've pretty much run out by now. Obviously, there are more Batman villains, but not any of significance that I know of. As of February 2009, no one is confirmed as a villain. Not the Johnny Depp Riddler, not Phillip Seymour Hoffman Penguin, nobody.