We covered the screen capturing app for Windows Phone Mango not so long ago, but it's noted that the app is not able to take screen shots of games. The guys at Nanapho.jp have come across an easy work around that involves little effort.
As one can see in the above photo, simply using the multi-task functionality, the user is able to save the screenshot of the game while in the task selection screen. Then simply use a photo editor to rotate and crop the image. There is a downside to this, as mentioned in their article, where the resolution of the captured images are 432×259 instead of 800x400. Check out an example below.
As well as gaming, this technique works when using the camera app as well as watching a movie. There's a slight sacrifice, but the functionality is worth it.