What is your favourite Firefox plugins you really really have to install ? You know, those which add functionality and should have really been part of Firefox ?
Adblock plus blocks those annoying ads. After restart you must choose one subscription that matches your country. The first one works fine for me.
Personas adds a nice “theme” to firefox. Firefox themes are usually limited to firefox buttons whereas Personas change the background of Firefox window from that boring grey to something exciting.
Leave comments on what plugins you find useful for all and I will update my list.