With the advent of the smaller car accessory flux capacitor from Think Geek, I think a "life size"
version that can act as a blue tooth speaker and 2A USB charger would be a cool build. Where the light
paths act as a visualizer for the audio (to the degree possible). Maybe powered by a Raspberry Pi or other SBC
with an small LCD / controller in the back that can also play media from onboard as well.