I know that many here uses Opera but also Mozila Firefox is a good Browser.

Well, here you can see the best and useful add-ons for Firefox. (my opinion)






FireBug - Website debugging tool


https://addons.mozilla.org/en-US/firefox/addon/1843


TorButton - Proxy button


https://addons.mozilla.org/en-US/firefox/addon/2275


Ad N Edit Cookies - Cookie editor


https://addons.mozilla.org/en-US/firefox/addon/573


Server Spy - Server software viewer


https://addons.mozilla.org/en-US/firefox/addon/2036



Modify Headers - Header Editor


https://addons.mozilla.org/en-US/firefox/addon/967



User Agent Switcher - switch the user agent of the browser.


https://addons.mozilla.org/en-US/firefox/addon/59



XSS-Me - XSS auditing plugin


http://www.securitycompass.com/explo...ssme-0.2.1.xpi


Access-Me - Test for Access vulnerabilities



http://www.securitycompass.com/explo...cessme-0.1.xpi


SQL Inject-Me - SQL auditing plugin


http://www.securitycompass.com/explo...sqlime-0.2.xpi


Advanced Dork - gives quick access to Google's


https://addons.mozilla.org/en-US/firefox/addon/2144


HackBar - Penetration testing tool


https://addons.mozilla.org/en-US/firefox/addon/3899


Live HTTP Headers -

* Help debugging web application.
* See which kind of web server the remote site is using.
* See the cookies sent by remote site.


https://addons.mozilla.org/en-US/firefox/addon/3829


NoScript - The best security you can get in a web browser!


https://addons.mozilla.org/it/firefox/addon/722


If you know any better you can always add it.