Firefox extensions

Favorite Firefox Extensions
I have been a Firefox user now for about one year. I really like they way the browser works, and I am not in a big hurry to try IE 7.

That said I just recently started trying extensions for Firefox. The two extensions I like most are FoxyTunes, that lets you control you media player right from your browser, and PacMan.

Why is controlling music from your browser important, well it really isn't, except I do read a lot on line. Working in software development there is always learning that needs to be done. I read a lot online and while doing so I listen to music. It is very convenient to be able to control volume and song selection without ever leaving the web browser. I never lose my place anymore and re-read the same paragraph multiple times.

I like the PacMan extension because well I like PacMan. It is nice to take a quick break and just play a fun 80's video game.

Some of the other extensions I use are ...
DOM Inspector
and
Firebug

As you can see I do not have that many, which brings me to a question. What extensions are you using and why should I want to use them?