Paste to Tab and Go Requires Restart
Paste URL or text to any tabs or a new tab and load it immediately, like 'Paste & Go' feature, but unlike 'Paste & Go', this extension will paste text from clipboard to a tab without focusing on the tab first.
CloseTab Requires Restart
Lightweight add-on which adds to right-click menu 3 items allowing to close current tab, open a new one and reopen closed one. Right-click anywhere on site instead of using keyboard or finding buttons.
Prevent duplicate tabs. Allow only one tab for a url. If you click a link that is already opened in a tab, then existing tab would be focused instead of opening a new tab. This works even across firefox windows.
Shift+LeftClick XUL Requires Restart
This simple addon has only this functionality, nothing else: it opens links in a new active tab with Shift+LeftClick (left mouse button click).
Better use https://addons.mozilla.org/ru/firefox/addon/shiftleftclick-opens-links-in-/ for FireFox.
Reopens the last closed tab.