This is the current list of Firefox Add-ons that I am using at work. Sharing here out of (possible?) interest (and so I can have a backup). They are all available via https://addons.mozilla.org/en-US/firefox/.
Auto Tab Discard - Automatically discard inactive tabs to free up resources
Gesturefy - Mouse gesture addon, which supports over 60 different commands and additional features like rocker and wheel gestures.
HTTPS Everywhere - encrypts your communications with many major websites, making your browsing more secure.
Privacy Badger - automatically learns to block invisible trackers. Be warned - it's good at breaking sites!
Shorten me - URL Shortener - shortens links and current tab's url using goo.gl service.
Tree Style Tab - provides tree-style tab bar, like a folder tree of Windows Explorer. New tabs opened from links (or etc.) are automatically attached to the parent tab. If you often use many many tabs, it will help your web browsing because you can understand relations of tabs.
uBlock Origin - an efficient blocker. Easy on CPU and memory.
YouTube High Definition - let's you play all YouTube videos in HD and change video player size automatically.