Ah—my favorite is in there:

https://tluif.home.xs4all.nl/chescom/EngExcPhanF.html

It’s a “robotic” board that moves the pieces by itself.

You can sometimes find “untested” (i.e., broken) ones on eBay for a reasonable price, and if you’re lucky they’re an easy fix. Mine was stuck because the lock slider had wedged something and the repair took all of 10 minutes.

Very clean engineering: a few screws gets you in, there’s a remarkably small PCB, few wires and mechanical pieces: the main mechanism consists of two orthogonally mounted sliders with a stepper motor and belt each.

I don’t even play chess, but it’s amazing to watch it play both sides.

They also use a clever algorithm to route pieces around other piece since (obviously) the pieces can’t jump over other pieces given that they are moved by a magnet under the board.