https://www.youtube.com/watch?v=vWyjLh0BB9o

Jurica Pranjic on MyMiniFactory was nice enough to share his rendition of the Titanfall Arc Grenade and when I found it, I decided I needed to have some fun with it. His version is a static prop, so I set about hollowing it out and redesigning it to accept the electronics I had in mind. I sent him a quick message and he was okay with the idea, so I'm sharing the results here.

Each of the eighteen arc 'plugs' has been bored out to accept a 5mm discrete Neopixel LED (or comparable WS2812 LED). The middle of the grenade has been fitted with posts on the interior that snugly slot a 9v battery inside the grenade, with enough extra room for a wire lead connector. The connector in particular I designed this around was a 121-0526/T-GR, but any T-shaped 9v clip should do. I changed the top handle to screw down with four M2 screws onto the body of the grenade so that the 9v could be easily accessed and swapped out.

An arduino (probably a 5v Adafruit Pro Trinket) can be hot-glued to the inside of the grenade, along with a piezo buzzer for sound effects. Two holes were added to the top of the grenade - one for a slide on-off switch, and one for a tactile push-button that will 'arm' the grenade.

The power switch hole is sized to accept an OS102011MS2QN1 slide switch. It does not stick out too much from the top of the grenade, which is fine, because I didn't want it accidentally turning on. The 'Arming' switch is sized for your standard tactile pushbutton.

In discussing this in the comments with others, I've come to suggest that a 5v regulator be added between the battery and the +5V input lines on the neopixels. It is otherwise fairly hard for an arduino to drive so many RGB LEDs at once.

I also added six alignment holes to make sure the grenade halves keyed together properly during assembly.