Using only a couple of servos, a laser module, some hot glue, and a microcontroller of your choice, you can easily build your own laser turret to annoy your cat.
These Learn to Solder kits from Rocket Dept. are a great way to teach your youngsters about soldering and basic electronics. One of them controls three LEDs with push buttons, one is a large RGB LED connected to three potentiometers so you can customize the color, one is a bug that vibrates to walk around, and the other is a firefly in a jar.