Blink any color you need! Use the Tri-Color LED board as a simple indicator, or by pulsing the red, green, and blue channels, you can create any color.
The tinyCylon is a multi-mode LED Larson scanner kit with five LEDs that blink or glow in various patterns.
The Lux Spectralis is a deluxe RGB blinky that you can build, with over 30 flashing, blinking and glowing modes.
These consist of a bright LED and flexible twisted lead wires that have a 2 slot female connector on the end (which can be removed).
A nice, compact 5mW green laser. Fun, but don't point in anyone's eyes.