Halo: Reach. Bungie forum user "Canuckian" discovered the short (embedded after the break) by poring over the code from the "rememberreach" ARG, where a handful of Windows Media video file names were found. After replacing the first ARG video's URL with the names of the WMV files found in the code, only one video worked: "Patrol."
In the clip, a trio of UNSC troops engage in brief, hurried discussion about the civilian rebellion on Reach and Noble Team's efforts to calm the "insurgents." The other videos -- "balloon," "hybrid long," "hybrid short," "new life," and "spaceport" -- aren't functional as of right now, but presumably will go live as we draw closer to the Halo: Reach launch.