Best firefox Extension for Web Developer

Here are the list of Firefox add-on plug-in I had been using for a while to test and debug for websites that I had been implemented, and not only that I can view a lot of buggy bad written Javascript (infinite loop) that make my precious Firefox Hang!!.
I think it is the perfect combination plug-in that a web developers must HAVE :

Web developer : A set of web development tools to help you imporve your coding, testing and debug.
Best tool ever. Get it from Web developer plug-in website.

Cache Viewer :Another great tool, to check the content of caches your browser are stored and track
the storage capacity was used. Basically it the GUI version of about:cache.
Get it from Cache Viewer plug-in.

Live Http Header : View Http header while browsing the web. Good to track the website you are visited.
Some say this tools can help you to track the port for private wifi WLAN such as
airport or public place but i haven’t try it yet. I used it to track the content send out
to the websites. Get it from Live Http Header plug-in.

FireBug : Ah, the master piece of css and javascipt plug-in to help you edit, debug and monitor the
performance of your script running on browsers. I really like this tool, because you can even
edit and execute javascript on the fly. Get it from here.