Comment or DM me to add to the list:
See: http://seriot.ch/parsing_json.php - Parsing JSON is a minefield. Notice how all of these json parsers are not up to spec. If they can't get it to spec then imagine the possible security issues with a format as simple as JSON.
JSON - Extremely Popular and Supported. Relatively easy to read.
XML - Old and Ugly. Widely supported. Useful if you need namespaces.
YAML - Popular format with Ruby and other server stuff. Apparently, a pain to implement and known to be insecure.
TOML - Simple configuration format. Some similarities to json. Complex arrays of objects suck tho.
HOCON - Extremely flexibile version of json.
JSON5 - Another flexible version of json. Not as flexible as others, but it has most of the important features.
HJSON - Flexible version of json.
LIBUCL