Major Nelson just confirmed on his blog that three games and a bunch of Just Dance 2014 songs have been discounted on the Xbox Games Store on Xbox One. There's 33% off EA Sports UFC, and both Metal Gear Solid V: Ground Zeroes and Titanfall are half-priced (Titanfall Expedition DLC is also 30% off).
On top of that there's a variety of Xbox 360 games that have been discounted. From Lightning Returns: Final Fantasy XIII to Risen 2: Dark Waters. Click through the above link to see the specific discounts, or switch on your Xbox. Either way it's up to you.