My sister and I are a big fans of Iron Man. I promised her that one day I will build her an arc reactor replica. Once I've got a 3d printer the time was right to build it! It supposed to be a birthday gift for my sister. However, I overshot the deadline by two months and it became a Christmas gift.
The heart of the arc reactor is Arduino MKR1000. It's a pretty neat small Arduino board with WiFi module built in. I added SD card to store the network settings and web page, and an OLED screen display to show reactor's status. For LEDs I used Neopixels' LED rings.
The case was 3D printed.
The reactor is powered via USB cable. Once powered, it tries to connect to the wifi network specified on the SD card. If it is able to connect to the network, it shows the IP address on the OLED screen. When you open the IP address in the browser you get a web page from which you can change the reactor's colour, brightness or turn it on or off.