Firefox add-on(s) for software developers and testers

I am listing out extension which I found useful during day to day software development and testing.
Feel free to add your comments to add any extension that you might find useful.

One liners are provided only against few extensions where it makes sense.

CLICK on each extension below to find out more about them.

+ Firefox Accessibility Extension 1.4.5.0 

+ Web Analytics Solution Profiler/Debugger (WASP) 1.10 – Extension for web analytics professionals

+ Molybdenum 0.6.5 - A web test tool. 

+ iMacros for Firefox 6.1.1.4 - Automate Firefox. Record and replay repetitious work

+ HackBar 1.3.2

+ YSlow 1.0.2 – Analyze web page based on Yahoo's rules for high performance web sites

+ Tamper Data 10.1.0

+ Greasemonkey 0.8.20090123.1

+ User Agent Switcher 0.6.11

+ Firebug 1.3.3

+ FirePHP 0.2.4

+ JavaScript Deobfuscator 1.5.3

+ IE Tab 1.5.20090207

+ Web Developer 1.1.6

+ Extension Developer 0.3.0.20080526

+ Codetch 0.4.1rc1

+ Regular Expressions Tester 1.1.6.12