https://www.worldtimebuddy.com/ - World Time Buddy (WTB) is a convenient world clock. Great tool.
https://www.joydeepdeb.com/tools/find-replace.html - Bulk text replace, great tools to make multiple replace in text or code.
https://getsharex.com/ - Best Free Screenshot Tool.
https://blaze.today/ - Quick Text snippets
https://clipclip.com/ - useful management tools for clipboards
Open Multi Tabs - https://chrome.google.com/webstore/detail/open-multiple-urls/oifijhaokejakekmnjmphonojcfkpbbh?hl=en
Live CSS Editor - https://chrome.google.com/webstore/detail/live-editor-for-css-less/ifhikkcafabcgolfjegfcgloomalapol?hl=en
https://www.caniemail.com/ - Guide of usage CSS in Emails.
https://milled.com/ - Most of emails in one place. Useful for designers. https://reallygoodemails.com/
https://www.omnisend.com/subject-line-tester/ - Test your subjects