Polytron, the developer behind the Xbox LIVE bestseller Fez, revealed via their Twitter that the game will be on special offer until tomorrow. You will be able to get the game, which is usually 800 Microsft Points, for half the cost at 400 MSP.
Earlier in the year, Fez went on to win Best Original Score and Best Indie Game at the Inside Gaming Awards. It did extremely well at a time where "perspective" games were insatiably popular, I think it's fair to say. The only other game that immediately springs to mind in this little niche sub-genre that also did well for itself was Pushmo on the Nintendo 3DS eShop, a game that was hailed by Nintendo fans and critics.
For those interested you can download the 273.45 MB game right from the Xbox LIVE Arcade marketplace.