Halo: Spartan Assault is out for Xbox One, for £11.99 in the Store.
Also out now is
Max: The Curse of Brotherhood, £11.99 in the Store. It's a reboot of the earlier Wii game Max and the Magic Marker.
I've not seen any reviews yet for the X1 version of Spartan Assault, but the Windows version was received quite well. From what I've read, it was praised for its graphics, gameplay, and Halo look & feel, with the main negatives being the touchscreen controls (not an issue on X1) and microtransactions.
Max has had some mixed reviews so far. Some solid 8s and 9s, but also some 6s.