This screenshot is from the "Classic Edition" of the 2D XNA demo game of Pong that I used for several presentations at DevTeach Montreal 2007, Toronto Code Camp 2007 and the NYC .NET Developers Group in September 2007. It is based on the Pong tutorial from the Game Camp materials created by Microsoft DPE Canada. It's not the most sophisticated demo around, nor is it the best XNA version of Pong (I like the one in Benjamin Nitschke's book), but it is simple enough for introduction-level presentations where you have only about 1 hour to explain what XNA is and demo its capabilities. I've gotten very good feedback for these talks, so I guess there's something people like here. You can download the demo files here.