This is a quick project I made several years ago.
A cool looking bat-shaped digital clock. The code runs on Arduino Pro Mini (clone) and additionally there is a RTC module, which is in charge of counting and remembering the time. The display consists of 4 8x8 red LED matrices.
Also my odd idea was to use an optoresitor to detect proximity/touch and in consequence display the current temperature. There is also DS18B20 temperature sensor connected via OneWire interface.