Terraria, Spelunky, and Fez. Putting aside if you can even call something a "modern classic," isn't that forgetting that whole other dimension of Fez? No, we didn't mean Phil Fish.
Anyway, we're not here to talk semantics: For today only, Fez and Spelunky are cut by 75 percent to $2.49 and $3.74 respectively, while Terraria digs down to a third of its normal price at $4.94. Also, don't forget the Xbox 360 Store has a whole bunch of games staying discounted across the week, including FIFA 14, Bioshock Infinite, and Castle of Illusion.