See https://en.wikipedia.org/wiki/Path_(computing)#Representatio... for a very incomplete list of examples.

Also "." was extremely common, used on large DEC systems (RSX, VMS) and Tandem/NonStop as home systems like RISC OS.

Multics and VOS use '>' as the separator (and '<' to indicate the parent).

The Multics-style paths really are the cleanest, in my opinion.

Edit: We run the Public Access Multics system at https://ban.ai/