The Last Minute weapon from Fallout 4 is a popular one. We recently looked at a different handmade replica of the rifle, and Kamui Cosplay, a.k.a. Svetlana Quindt, just completed one too. She crafted the modified Gauss rifle and wrote the code to light it. Kamui made it from mostly laser cut EVA foam and 3D printed parts. She used iron powder and hydrogen peroxide to give the prop that nice weathered look. She says:
The light effect was made with one meter of Neopixel LED strips (60 LEDs/meter), a Trinket pro 5V and a Powerboost 500c from Adafruit. I just edited the code from the Neopixel library for my animation.
It was powered by two 4400 mAh lipo batteries.
You can get the rifle blueprint from Kamui’s shop.