Some LEDs that blink in a stop light-like sequence.
I tried to make a smaller version of a street stop light with an Arduino, but that didn't really work, so I made a smaller version. I put some green, yellow, and red LEDs onto a small breadboard, then hooked then up to the Arduino Uno that I use. I used the Arduino GUI to code the lights to blink like stop lights, then uploaded it and stood back to watch! It's simple to make, really.