Chris Bryan has recreated what looks like a few seconds from the Halo 2 announcement trailer with what one imagine might be Halo 3 quality graphics-- entirely from scratch (no extracted content). HBO has versions in QT and WMV formats. It's a small download, but quite impressive and well worth it. Thanks Louis Wu.

UPDATE: Blackstar added some audio to the clip, and is hosting that version with audio at Blackstar Productions. (He still doesn't say anything, so "speechless" still applies--Ed.)