Postman - The Collaboration Platform for API Development
Requester - HTTP client plugin for Sublime Text with an expansive feature set, modern UX, elegant syntax and...
Sauce Labs - Test mobile or web apps instantly across 700+ browser/OS/device platform combinations - without infrastructure setup.
API Test Base - API test automation tool that has GUI, supports HTTP stubs (mock services), data driven testing, and API types beyond HTTP, such as relational database, JMS, FTP(s), AMQP, MQTT, etc.
TestComplete - TestComplete Desktop, Web, and Mobile helps you create repeatable and accurate automated tests across multiple devices, platforms, and environments easily and quickly.
Postwoman - An online, open source API request builder