gutupio has posted a link over in the HBO forum to what just might be the first true 100% HUDless Halo film. (Silvergrunt earlier did a WMV with HUDless clips in it, and others may have as well.) It's a 20 Mb DivX-encoded AVI, and reportedly the closest it has to a title is Entry 1, which seems to suggest to me at least the theoretical possibility of an Entry 2 at some point.
We've added a mirror of Entry 1 in our Halo Movies section.