Selenium - Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that.

Postman - The Collaboration Platform for API Development

Cucumber - Cucumber is a BDD tool for specification of application features and user scenarios in plain text.

Postwoman - An online, open source API request builder

Ranorex - Ranorex is a GUI test automation framework for testing of desktop, web-based and mobile applications.

Endtest - Intelligent Test Automation