SpeedS@ver - Game Speed-runs as your Screensaver.
This is an imaginitively titled screensaver that will download and run videos of people completing speed runs of games. I for one don't really have time to play games anymore, but I can sure enjoy watching people who do, doing so.
This screensaver should work on Mac OS X 10.7 and above. However, it has only been tested with 10.8.
It will download a movie then continue playing every time the sceensaver loads until it finishes. There are options for which systems to download movies for, and which qualities to download from youtube. Or you can make it stream in the options.
Download this zip file - unzip - double click the .screensaver. That will install it and open the System Preferences where you can choose the screensaver.
In order to build this I built a Screensaver Bootstrap app that emulates the Screensaver app whilst making it super easy to iterate fast on a screensaver. If you're building a screensaver this is really useful - especially as it means you can use the debug tools in Xcode.