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.
Cucumber - Cucumber is a BDD tool for specification of application features and user scenarios in plain text.
Ranorex - Ranorex is a GUI test automation framework for testing of desktop, web-based and mobile applications.
TestComplete - TestComplete Desktop, Web, and Mobile helps you create repeatable and accurate automated tests across multiple devices, platforms, and environments easily and quickly.
Endtest - Intelligent Test Automation
Capybara - Capybara helps you test web applications by simulating how a real user would interact with your app.