The last thing I did was the Hyperion light project for my TV and connected game consoles. Involves a Pi, Arduino, HDMI splitter, a bunch of ws8212 RGB LED's and this USB to component doodad. Takes any input source on HDMI and feeds it to the Pi. The Pi then reads the color of the pixels on the edge of the screen and outputs that info to the Arduino which then uses a few pin outs to match the LED colors to the pixel colors.
Super unnecessary and I inevitably spend some inordinate amount of time troubleshooting it every few months, but playing games on it is an absolute blast.
I'm on work computer right now so I don't have my video of it, but this one is pretty much exactly how it looks.
I know there are some avid Pi guys out there so I'm curious what other projects you're working on or have got planned. Always looking for a new way to waste my weekend.