Halo: Reach promotion at 1,100 stores across the United States. The event seems to revolve around a video featuring an MLG guy giving tips and tricks for Reach (that you can't use yet), along with supposedly new in-game footage and a raffle for a Legendary Edition of the game (that you can't take home until launch day).
There will also be "text-to-win sweepstakes" for an opportunity to win a life-sized Halo statue. The marketing opportunity begins Friday, August 6, at 9PM (local time) and lasts 90 minutes. GameStop has a page to check whether your local locations are hosting the video vignette and raffle.