• Adblock µBlock uBlock Origin : should I have to explain?
• ColorfulTabs : nice colors in your tabs
• Flagfox : Displays a country flag depicting the location of the current website's server and provides quick access to detailed location and webserver information
• Greasemonkey : Allows you to customize the way a webpage displays using small bits of JavaScript (see below for the scripts I use)
• Neo Diggler : add a “clear url bar” button, along with some nice shortcuts, similar to Konquefox, but Firefox 6-compatible
• Tab Preview : shows a preview of tab contents
• User-Agent Switcher : adds a menu and a toolbar button to switch the user agent of the browser
• Ghostery (and Collusion) : because privacy matters
• Searchonymous : “Search anonymously on Google, while keeping your search preferences and stay logged in on services such as YouTube, Gmail, etc.”
• Wappalyzer : Tells you what software is used on the current visited website
• RequestPolicy Continued : Protect from ligatus/outbrain/etc. crap
• Channel Blocker YTBlock : remove channels from YouTube video suggestions
• SponsorBlock : Same as your favorite ad blocker, but for YouTube videos' sponsored parts
• YouTube No Translation : prevents automatic translation on YouTube
• AutoAuth : Automatically submits HTTP authentication dialogs when you’ve chosen to have the browser save your login information
• Shaarli Shaanti : add a Shaarli button to bookmark delicious links
• Two Factor Authenticator : Generates TOTPs for 2 factor authentication (Google Authenticator style)

• Google's Old Favicon : because the new one sucks
• Google+ Old Favicon : same thing, but for g+
• HQTube : automatically selects the HQ version of a Youtube clip
• Check Range : allows to check multiple check-boxes at a time, using shift+left click
• FreeMobile : restore legacy login form on Free Mobile's website
• Disable Youtube Autoplay: because I don't want a fucking jukebox
• Disable Youtube next video autoplay: same as above, but for next video (unfortunatly the first one does not seem to work for that)
• YT - Overlay remover: hide cards/overlays on youtube videos not working (anymore), use “www.youtube.com##.ytp-ce-element” in uBlock instead
• YouTube: Age Verification Bypass: yeah, I'm old enough and I do not want to login
• The Ultimate Popup Blocker: hope it will block all these JS silly popups…
• Pinterest without registration: allows to browse Pinterest without login/registration, removing the offending modal popup (see below for Facebook)
• Facebook and Instagram login popup remover: same as Pinterest but for Facebook & Instagram, obviously.
• Instagram Download Button: add the download button and the open button to download or open profile picture and media in the posts, stories, and highlights in Instagram

For Facebook:

• replace smileys : Replace text smileys with graphic ones
• Facebook Fixer : a.k.a Facebook-on-steroids
• Chat Killer : web is not for IM. Get a real client, and use Jabber.
• Friends Checker : Regularly checks your Facebook friends to check whether anyone has removed you from their friends.
• Nickbook : personal script to hide avatar below the comment box

• Manually sort folders : sort account folders
• Firetray : display number of unread messages in the tray bar
• Lightning : Calendar for Thunderbird
• Provider for Google Calendar : sync Google Calendar with Lightning
• Exchange 2007/2010 Calendar and Tasks Provider : the perfect companion of Lightning, for those living and working under MS Exchange oppression.
• Google Contacts : adds Google Contacts address book
• Mailbox Alert : customizable notifications
• Smiley Fixer : “Fixes Wingding Smileys in Outlook-generated emails”
• SOGo Connector : easy way to do [Cal|Card]dav in Thunderbird
• CatchAll Bird : handles incoming messages addressed to all prefix@domain.tld for a fixed domain. for each prefix the AddOn can create a new identity and folder.