Elasticsearch: it accepts JSON bodies in GET requests to define the parameters of a search. These can get quite large so it's preferable to encoding everything in the query string. The operation is read-only, so an argument can be made that a GET makes more sense than a POST.
That said, I POST my search params to Elasticsearch anyways.
Is that really restful though? If you need that many parameters to specify which resource you mean, you lose pretty much all of the benefit of a restful architecture.
GET vs. POST is a question of whether the request is intended to change state. Using JSON for a query is nice for preserving structure (e.g. nesting a Boolean expressions, not needing PHP-style array notation, etc.) but it doesn't change the idea that it's a GET request which can safely be repeated without affecting server state, may be cached for other clients, etc.
That said, I POST my search params to Elasticsearch anyways.