The hunter

[WindexGlow]

You poor fool.

DownloadThemAll
https://addons.mozilla.org/en-US/firefox/addon/201
I enjoy this one, don't use it too much though.

Adblock
https://addons.mozilla.org/en-US/firefox/addon/1865
Couldn't live without it. Blocks ads like no other. Pages are so much cleaner.

NoScript
https://addons.mozilla.org/en-US/firefox/addon/722
Also couldn't live without it. Blocks javascripts, but incredibly easy to use. No more random sites blaring music for me.

Stumble Upon
https://addons.mozilla.org/en-US/firefox/addon/138
Get it. Now. I was skeptical at first, but it works incredibly well.