Smoothlife (paper, source code is a floating-point version of the old Game of Life, a classic of evolutionary computing and genetic algorithms. By adding floating point math to the mix, Smoothlife produces an absolutely lovely output:
SmoothLife is a family of rules created by Stephan Rafler. It was designed as a continuous version of Conway's Game of Life - using floating point values instead of integers. This rule is SmoothLifeL which supports many interesting phenomena such as gliders that can travel in any direction, rotating pairs of gliders, wickstretchers and the appearance of elastic tension in the 'cords' that join the blobs.