The Cosmicar/Pentax TV Lens 25mm f1.4 is a tiny C-mount lens designed for security cameras. With an appropriate adapter (not included), it comes reeeeeal close to covering Micro Four Thirds (with minor vignetting). Obviously this isn't a lens you're going to turn to for technical work, but image quality at the centre is pretty decent, and the distorted edges are kind of, y'know... fun.