What is your favorite firefox plugin?

StumbleUpon. Thats the best and my favouraite. It automatically returns websites from your interests and make surfing a breeze when you are bored. I like it because it always returns funny and hilarious stuff along with informative stuff too. Its a very good plugin in which you can store your fav web sites for later reference and also send the ones you like to a friend who would also like it.. bourne

I have so many! ... I would say No-Script is my favorite. My toughest guard for my online activity. No script activity will run without my approval, It has a remember feature for those that I really trust like myLot and Yahoo. My 2nd best is Download Statusbar, this make my downloading a lot simpler, much better that the default or built-in download manager.

I like NoScript best because I surf the net a lot and I don't want any malicious scripts get chance to run on my computer. This fasterFox, is it an official plugin of FireFox? I mean, has FireFox certify that it is "clean"?