Keychain of the arc reactor Iron Man uses in Iron Man 2, The Avengers, and Iron Man 3.
Ideal for 3 color changes: Blue, white, and black (or gray). I used glow-in-the-dark blue for the base color and it turned out great. It glows in the dark after shining a light on it. Also, it allows light to pass through and makes it look straight out of the movie.
Enjoy and please share pictures if you make it!