The first documented actual human injury sustained while playing with Kinect is quite a doozy.
It was bound to happen sooner rather than later with how frenetic your actions are when you play a game with Microsoft's Kinect for the Xbox 360. Other than the emotional injury of Dance Central recording you naked, and the property damage from a Kinect player bombarding his TV with a ceiling fan pullstring, a video depicting a young man getting an elbow to the face from his father seems to be the first bodily harm caused by Microsoft's peripheral. The video was uploaded on November 4th, the day that Kinect was released in the US, and it's amazing.
I love the contrast of the first 20 seconds of wholesome family fun. The sun is shining in through the blinds, and the mother is clearly enjoying watching her husband and son playing together. It seems like something out of a modern day Norman Rockwell painting.
That is, until Dear Old Dad throws his elbows back and connects with his son's face. The Mom shrieks in terror, "Oh my God," and if you listen close you can hear moans and grumbles from the injured kid before the video cuts out Cloverfield-style.
I'd be lying if I said I didn't watch the moment of impact about 25 times in succession. It's just good, clean fun!