Everyday use :
a filter subscription when Adblock Plus starts up the first time, then even this simple task will usually be unnecessary: the filter subscription will block most advertisements fully automatically
Colors every tab in a different color and makes them easy to distinguish while beautifying the overall appearance of the interface. An essential...
This plunging blocks any flash contains on web page. which is quite useful if you want to save bandwidth.
Tab mix plus
you can have as many tabs as you like. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager with crash recovery that can save and restore combinations of opened tabs and windows.
McAfee SiteAdvisor for Firefox 26.5
SiteAdvisor helps protect you from all kinds of Web-based security threats including spyware, adware, spam, viruses, browser-based attacks, phishing, online fraud and identity theft.Download Statusbar
View and manage downloads from a tidy status bar - without the download window getting in the way of your web browsing.
Web developments :
allows you to debug the scripts. useful if you are doing web development. ( where you don't want to invest in heavy duty, high cost tools)
better then conventional source code viewer. this shows coloured
Internet Security :
this blocks any script execution from webpage. like scripts which can execute lunches something. you can block/give permission by using local link ( which is a strong consequence of Internet explorer )