Google Gmail Video
Who better to promote Google's products than Google engineers themselves? The centerpiece of open sign-ups campaign is "Gmail Theater," a series of four short vignettes in which Kai, a Gmail engineer, introduces a homemade (or, to be more precise, office-made) puppet show which uses found cubicle objects to demonstrate the benefits of four key Gmail features in a "lo-fi" manner.
Art directed the video that became viral reaching 1M views in the first month of it's launch.