Some additions to your list (disclaimer: I’m an employee at Applitools and a co-founder of Sauce Labs):

1. Applitools — AI powered visual testing that addresses some long-standing pain points around test maintainability and execution speed. www.applitools.com
2. Sauce Labs — arguably the industry standard for cloud functional testing. www.saucelabs.com
3. Perfecto and CrossBrowserTesting — both Sauce Labs competitors. https://www.perfecto.io/ and https://crossbrowsertesting.com/
4. Appium — what Selenium is to web app testing, Appium is to mobile app testing. Open source and widely used. http://appium.io/
5. Cypress — generating lots of interest in the testing community. https://www.cypress.io/. This blog post explains some of the differences between it and Selenium: https://applitools.com/blog/cypress-vs-selenium-webdriver-better-or-just-different

Hope this helps!