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.
Oni - An IDE powered by Neovim
UI.Vision - Modern open-source task and test automation tool and Selenium IDE.
GraphWalker - GraphWalker is an open source Model-based testing tool for test automation. It's designed to make it easy to design your tests using graphs.
TestComplete - TestComplete Desktop, Web, and Mobile helps you create repeatable and accurate automated tests across multiple devices, platforms, and environments easily and quickly.
Kantu for Chrome and Firefox - Modern Open-Source Web Macro Recorder and Selenium IDE.