Firefox user, do you remember this! When Firefox 4 was released, by turning about:config preference browser.ctrlTab.previews value to true (from default false), we can able to cycle tabs open in Firefox, in recently used order by pressing Ctrl+Tab. This hidden preference still exists and disabled by default, to expose this to the user, Mozilla has now enabled it and added a new preference to Tabs settings in Firefox 50 Nightly, deactivated by default though.
To spot it, in the latest Nightly, click on menu > Options> General and check Tabs for the new setting: ‘Ctrl+Tab cycles through tabs in recently used order. To see the feature in action, enable it and press Ctrl+Tab.