If you're looking for an action/arcade game for your Windows Phone that is a tough nut to crack, take a look at Couplinked.
The game has you controlling two nodes (or dots) that are connected by an electrical field. Your job is to collect colored rings that are flying across the screen with the corresponding node you control. You also have a red ball that flies through from time to time that will ruin your day.
Available for low-memory devices, Couplinked may not appeal to everyone but there's little doubt that this is a Windows Phone game that is frustratingly challenging.