Most Useful Firefox Addons' For Hacking

FFMyIP : show your current public IP and can alert you when it changes
Download

HackBar : A toolbar that helps you to find and test SQL injection and to manipulate URLs
Download

HeaderSpy : It shows HTTP header in the status bar
Download

Access ME : This extension helps to test access vulnerabilities on website through session tampering.
Download

Add N Edit Cookies : A cookie editor
Download

JSview : Show the source code of every extern Javascripts and CSS used on a webpage
Download

ShowIP : show the IP of the current website in the status bar and allow simple whois/netcraft request.
Download

SQL Inject Me : This extension test SQL injection Vulnerabilities of every form of a page.
Download

TamperData : A live HTTP/HTTPS header editor.
Download

XSSMe : Same as SQL Inject Me for XSS vulnerabilities.
Download

And a brain of course !! But I didn't find any link for this one...

p/s : hehehehehe...