Digital Dent
I've been told by a rock-solid source that Cinesite in London are to be handling the CG FX for Two Face in The Dark Knight, with their work due to start in earnest in November. I mention this just so you know it isn't an entirely make-up based look.
[EDIT: Actually, my source has read this published post and told me, actually, it's Framestore CFC and I 'misinterpreted their clues' to the FX house. My mistake, and quite a dumb one, really. I could explain the confusion in how I thought they meant one and not the other, but they asked me not to, as it might just reveal who they are...]
But why not make-up, I wonder? The only solid reasons I can think of are all mouth-based - teeth showing through a wound, maybe, or impossible mouth movements. But I don't know for sure. Hopefulyl more info will be forthcoming.
Cinesite are, frankly, brilliant and have a great back catlogue of work - from Charlie and the Chocolate Factory through The Hitchhiker's Guide to the Galaxy to Hot Fuzz.
[EDIT: And Framestore CFC are similarly excellent, if not more so. Their work on Children of Men is amongst the greatest FX work ever completed. As well as the digital Dent they'll also be creating the virtual set extensions for the Hong Kong scenes and some CG stand-in Batmen]