See also: https://en.wikipedia.org/wiki/Ferroelectric_RAM, which has been used in a few quite popular systems as well (e.g. the PS2 memory card supposedly uses it for some high-rewrite-count operations).
FRAM is also used in all modern MSP430 microntrollers from Texas Instruments. Amazing technology
MRAM (magnetic and non-volatile) had some applications in GBA cartridges to replace small amounts of battery-backed SRAM.