WOT – Safe Browsing Tool
Tab Mix Plus
Firefox Sync
FlashGot
NoScript
Cookie Monster
Flagfox
User Agent Switcher
Google Hangouts

Adobe – Flash Player: Settings manager – Global Storage Settings panel:

http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager03.html

Panopticlick tests your browser to see how unique it is:
https://panopticlick.eff.org/

Multimedia plug-in for Gecko browsers
aptitude install gecko-mediaplayer