There's tons of great deals today for the Xbox Live "Ultimate Game Sale," including Bioshock Infinite for $39.99, Metal Gear Rising: Revengeance for $29.99, XCOM: Enemy Unknown for $19.99, and Tomb Raider for $19.99. Infinite probably needs no introduction, but specifically, XCOM was one of my favorite games of 2012, and Tomb Raider and Revengeance are two of my absolute top games of 2013, if you're looking for recommendations.
Also on sale are Gears of War Judgment for $29.99 and Hitman Absolution for a cool $9.99. Keep in mind that you can get some of these cheaper on Steam or used in physical form (or on PS+), but comparison shopping wise, some of these deals are pretty damn good.
Xbox Live [Major Nelson]