I'd personally say that Catwoman is the most obvious choice as she's always played something of a love interest for Batman, though she's not usually what I would call a threat to Gotham. I'd say maybe Talia Al'Ghul could make an appearance. It'd make sense for her to be out for revenge on Batman.

Quote Originally Posted by I Don't Need A Name
the most feasable enemies would be the likes of The Penguin or Riddler
I disagree with the Penguin. He was always more of a gangster in the comics, and any take on him that involves having him associated with actual Penguins is an obvious no go. I just can't see them playing the Gangster angle Batman's war on the mob played so heavily into Begins, and even more so in The Dark Knight. I think iot'd feel kind of like retreading the same old ground. I'm sure if Nolan included him I'd be very pleased with how he was used, but I guess I just never liked the character to begin with.