I interned at a company that used an s-expression format as an alternative to JSON and it was great—much better than any mainstream format for config files and

I interned at a company that used an s-expression format as an alternative to JSON and it was great—much better than any mainstream format for config files and human-readable representations for API data. It was great at representing structured data (including tagged variants, so full algebraic data types) and even pretty good for text markup. It also has best-in-class editor support thanks to paredit :) The only real downside is the hassle of convincing people to use something weird and non-standard, which is really more a problem with people than with the format.