A simple pin with a back-lit butterfly that slowly fades colors in-and-out. This is like a smaller, cheaper, easier to assemble version of my Neopixel Butterfly Brooch, here on thingiverse. Attaches to clothing with a magnetic clasp.

Powered by a CR2032 coin cell battery in a Lilypad battery holder/switch. The cover/lid snaps onto the case. Parts cost < $20 USD. Get the slow-fade RGB LED @adafruit

3D print time: about 2.5 hours
Assembly: < 45 min

See blog post at thisoldgeek.blogspot.com