The Cavalier is a Three Musketeers-type villain who is a skilled fencer, wielding an electrified rapier. I've only read two of his appearances, his original 1943 story, and a brief fight in Knightfall where the Cavalier doesn't even get a word out before being beaten down by Batman. In the issue where he did have lines, he spoke in a strange, colorful, and somewhat pompous English, strange even by old comics standards. I had to look up quite a few words (like varlet), so he's not only a Batman villain, he's educational! Recently, in some comics I didn't read myself, the Cavalier was revealed to be involved in a secret gay affair with Captain Stingaree, the realism of which was debated here. The gay thing really isn't surprising, in his inaugural appearance, Robin calls the Cavalier a "rainbow," which... may not have meant that at the time, but it's kinda funny in retrospect.
Pros: I'm drawing a blank here.
Cons: The very first thing the Cavalier ever said was "That baseball you coddle interests me mightily, stripling!" which tells you all you need to know about how well the character fits with the modern, semi-realistic version of Batman we see in the movies.
How I'd do it: Something like in Knightfall where Batman silently beats down a weird looking guy in a Three Musketeers outfit would have worked perfectly in the Tim Burton/Joel Schumacher movies, but it's a little too goofy for Christopher Nolan's Batman.
Casting Guesses: Will Ferrell. His dialogue in his initial appearance had me hearing Will Ferrell's voice in my head, reminiscent of his Black Knight character on that one Family Guy where he calls Peter a fizzle.
Verdict: Verily, though it pains me to say so, we shan't be seeing the Cavalier any time soon.
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.