Postwoman - An online, open source API request builder
Postman - The Collaboration Platform for API Development
soapUI - SoapUI Pro is one of the most prominent API testing platforms around, allowing developers to quickly prototype the functions of their apps and get them to market with little hassle.
Insomnia REST - The most intuitive cross-platform REST API Client ð´
RESTer - A REST client for almost any web service (Firefox and Chrome extension).
RESTClient - RESTClient can be used to test variety of HTTP communications and RESTful webservices.