OK, who said "easy" and "done before" wasn't fun too? I've been shooting light spots around my neighbourhood by using a Brownie Hawkeye and some Ektachrome 100S. I've let the shutter open, pointed at something, and tried to work on the specific resulting patterns by moving the camera in such direction. The results are interesting because with that technique you are "painting" with a light source, and therefore not completely random.
Of course everyone must have tried that at some point, but the result is so fun, that I wanted to share some.