Ask HN: What are exemplary REST APIs?

There are many good resources about writing APIs, but I'm also curious what the crowd here would consider great, exemplary REST API's? Looking for things like well-structured URI's, great design of request and response bodies, useful error handling, useful and beautiful documentation - as well as dealing with real-world stuff that can make API's and REST hard (pagination, wanting to do RPC style stuff specifically long-running tasks, etc.). Any good API's you'd recommend looking at for inspiration?