I built a thing which displays Conway's Game of life:

• Loop detection (starts with new random pattern when a loop has been detected)
• An LCD module displays the current generation number
• Extremely inefficient code: uses 100% CPU on three of the eight CPU cores in the Parallax Propeller for game logic, LED update and LCD update. :)
• Time-multiplexed 16*32 LED matrix display: at any one time, one row of 32 LEDs are lit