I have been playing, Fire My Laser - http://aka.ms/FireMyLaser, which I find to be a fun, challenging and engaging game for Windows Phone 8.  It’s built with the Unity engine and has good production quality.  One of the things like about this game is that it use of the Windows Phone/Accelerometer, to turn your player position.  The game provides a radar to show where the enemy is coming from and be aware (which I wasn’t initially) they come at you from 360 degrees.  I felt it had about the right about of difficulty. 

Use your Gyroscope/Accelerometer to defeat the invading undead army! 

Get it and provide the developer feedback http://aka.ms/FireMyLaser.