The EKI 2014 Robot Blinker Kit alternately flashes two pair of LEDS at a rate of about 2 flashes per second. This is a fun toy as well as a great way to learn how oscillators work.
9V battery not included.
Principles taught: RC timing, transistor switching.
Components: 4 resistors, 2 capacitors, 4 LEDs, 2 transistors, slide switch, battery snap