the only add-on you will not be able to use firefox without Rated 5 out of 5 stars
I first used Mouse Gestures with Opera along long time ago when Opera wasn't free. Ever since then I can not use any browser without mouse gestures.
If you don't know what Gestures are they are either PRE-program shapes you make with your mouse to affect your browser or custom made shapes. For example Down Left Down Left Down for me CLOSES ALL OTHER OPEN TABS....
For nice to be able to close 25 tabs at once and keep the one you are reading open.
The problem is if you use someone elses computer you will try to use your mouse gestures to go back and forward or close a tab and get that awful RIGHT MOUSE BUTTON menu.