In the actually used department of esoteric languages, there’s the TeX macro language. It’s Turing complete but also completely sui generis. Especially the whol

In the actually used department of esoteric languages, there’s the TeX macro language. It’s Turing complete but also completely sui generis. Especially the whole cat code aspect of the language where any character can have any significance and it’s possible to make inaccessible token sequences.