Shake and Save is a marvellous way to capture and save screenshots of your Windows Mobile device. Whatever screen or software is being run, simply shake your WinMo device to capture the image - there are options to save in the 4 most common image formats (PNG, BMP, GIF, JPG), and the application runs in the background.
Taking screenshots is always a useful function to have, and Shake and Save brings a nice bit of usability to this field. Download from FreewarePocketPC.net.
hdBoobs is as the name suggests an adult themed novelty application whose sole aim is to make a pair of ladies breasts bounce. It's a great example of how the g-sensor accelerometer functions - the more vigorous the shaking the more dramatic the on-screen movement.
Available from the developers website, like all examples on this page hdBoobs is free, and requires the Microsoft .Net CF 3.5 and Windows Mobile 6 or greater to run.
Magic 8 Ball (Let the Universe Guide You) is another fun application - the simple aim is to ask a question and shake your phone. A magic answer is produced as the result, which in theory will give you the needed guidance, but most likely give you a chuckly.
Download Magic 8 Ball from the developer's website.
Waterlevel is available from FreewarePocketPC.net and basically acts as a spirit level. The three meters on the top, left and centre of the screen measure your phone's position on the x, y and z axes allowing both accurate measurement and calibration of your g-sensor accelerometer.
Finally, Gyrator2 is a useful configuration tool for applying a screen orientation to your Windows Mobile applications,based on a range of events such as how your phone is positioned, what task is being performed, and so on. It's a very cool application and out of all of those listed here is probably the most useful.
Download Gyrator2 from the developer's website.