Thomas Blake was a big game hunter who, now bored of killing lions, decided to move to Gotham and take up costumed crime. He borrowed Catwoman's theme and costume (much to her chagrin) and named himself Catman. Many of his early stories relate to his competition with Catwoman. His cat-themed crimes are often falsely pinned on her, so she has joined forces with Batman to stop Blake.
Later, Blake was portrayed as a joke among supervillains, a loser even among those who always lose to Batman. So he and Killer Moth formed a team of D-list villains called the Misfits. Later still, Blake has joined the Secret Six, a group of villains including Deadshot and Bane.
As a hunter, Blake's abilities include tracking, hand-to-hand combat, and a number of weapon skills, and he has metal claws built into his suit.
Pros: No supernatural powers, so he's not a stretch realism-wise. That's about it.
Cons: His backstory is that he's bored and needs money, so he puts on a cat costume and steals stuff, which is pretty weak. And Catman in a movie would feel like a poor substitute for Catwoman.
How I'd do it: I think I'd just rip off Kraven the Hunter from Spider-man. Thomas Blake decides that the hunt for Batman is the ultimate challenge.
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.