Seems to be that oscilloscope can be used not for displaying signals only, but it also can also used as generic display. So there was Oscilloscope clock born.
Of course it would be ridiculous to put this scope-clock on you working desktop to show time, but it may serve as nice demo. From technical side this is fully functional clock running on AVR board. Signals are taken by using two 10x probes. Clock refresh rate can reach up to 250Hz. Firmware is written so that it prevents screen from burning-in(screen is automatically repositioned). Board itself has many features including battery backup, RS232 connectivity. It may also be interfaced with external GPS receiver. All files (including design and firmware) are available for download, but why not to buy tested and professional looking kit for only 25$.