Unconventional computing is computing by a wide range of new or unusual methods [including] … optical computing, quantum computing, chemical computing, natural computing, biologically-inspired computing, wetware computing, DNA computing, molecular computing, amorphous computing, nanocomputing, reversible computing, ternary computing, fluidics, analogue computing, human and domino computation.
I’d still like a mechanical computer, I guess they have been testing some new designs out: tomshardware.com/…/kirigami-mechanical-computer-h…
Domino and billiard ball computers sound like interesting “just for fun” designs: