While not practical for mountaineering situations, my favorite rappel device is the rappel rack;

https://www.rocknrescue.com/product/smc-nfpa-long-6-bar-rappel-rack/

Developed in 1967 and enhanced/improved since then, it is safe and relatively foolproof.

Most of my rappels lately have been down sea cliffs abd canyon walls to retrieve fossils, which I suppose is a relatively specialized use - also used by window washers, etc...