Firefox Ctrl+Tab Popup Menu Switcher
The Tab Mix Plus extension has a gem of a feature buried deep within the settings: The ability to turn the Ctrl+Tab key from a direct tab switch into a popup menu that works similarly to the Windows Alt+Tab feature. It’ll pop up a tiny dialog window that gives you a list of your tabs, and then on release of the keys will switch to that tab.
To turn on this setting, open up Tab Mix Plus Options, click on Events and then the Tab Features tab. You’ll see a checkbox titled “Ctrl-Tab displays a tab list popup menu” which you’ll want to select.