While leading up to it's release, Bungie began releasing some excellent and informative ViDocs for Halo 3, and they're following suit for it's stand-alone Expansion, Halo 3: ODST.
The first ViDoc, entitled "Desperate Measures," can be viewed below or here, and it takes a look at the Helljumpers under the command of Sgt. Buck.
Bungie has a history of releasing poorer looking (compared to other games) character models, but the faces on the ODST's are really looking good. Sgt. Buck actually looks a good bit like Nathan Fillion.