I might be a little late to this thread. I'm currently working on two robots, the first one is a hexapod that I'm rebuilding and reprogramming, using a teensy 4.0, while not technically an arduino it uses the arduino ide so I'll count it. The second one is a smaller autonomous rover with a lidar, it uses a raspberry pi 4b as the brains and has an arduino nano to move the motors and take movement commands. It runs on ros, and I can now click on a map in rviz to have it move there. Currently working on pathing. The plan is to move the lidar to the hexapod once I'm done with the rover and the hexapod.

So.. various things:

-an LED clock -dsp learning with a Nicla Vision (i want to learn how to implement digital filters and use them on the signal sampled from the on-board mic) -a custom keypad for special characters -a tool to use at work to check encoders signals