I have the following addons in Firefox.

Always on Top - Allows me to make a single window have always on top status for when I'm watching a video or something, needs an external application to actually do the WinAPI calls necessary and sometimes it doesn't really work as expected but it's neat when it does.
Ank Pixiv Tool - Allows me to save entire pixiv galleries (as well as a couple other sites) in one shot with metadata, I wrote a little web dingus that also uses said metadata. It's neat because for some reason Japanese artists like to randomly delete things.
Better TweetDeck - Makes TweetDeck better.
Better TTV - Apparently makes Twitch better, although I don't really use it a whole lot.
DuckDuckGo Privacy Essentials - One of three trash blockers I have (other being uBlock and the built in Firefox one).
ExHentai Passport - You don't want to make the panda sad.
Greasemonkey - Helps me make various sites less bad through userscripts.
Honey - Sign Up Now At Join Honey Dot Com Slash Flash Wave. Gets me small discounts sometimes, probably slurps up my personal data.
Rikaichamp - Helps a weeb out understanding the scribbles.
Song Identifier - Employs some kind of black magic and is able to tell you what music is playing in your browser window right now if you can't figure it out.
Stylus - Helps me make various sites less bad through userstyles.
uBlock Origin - One of my many trash blockers.
Youtube Full Windowed - Goes hand-in-hand with the Always on Top extension allowing me to have a video take up the entire window and have the window on top regardless of where I click.

Mine overlap with flash except for:

FrankerFaceZ- Lets you add custom emotes and use them on your twitch channel

FrankerFaceZ Enhancing add on- Just gives enhanced functionality to some options. Pretty minor

Youtube Dark Theme-I have a dark theme for youtube because I use the old one now, but I wouldn't recommend since its kind of poorly done.

Web Scrobbler- For scrobbling playback history with last.fm

I used to have more extensions but I got rid of some because I really don't use them anymore.

i have frank on my desktop as well, i guess i didn't install it from AMO

When i wanted to get it as I switched to firefox, I realized the extension was on chrome but on firefox you get it through the website.

im a simple girl, i only have HTTPS Everywhere and uBlock Origin, used to also have LastPass but ive switched off of that

I use GNU IceCat on Arch Linux

I use

HTTPS Everywhere with Forced HTTPS
uBlock Origin
uMatrix
IPvFoo

chromium

Decentraleyes - just stolen from rafuwu
Enhanced Steam - used to use it for paying uneven amounts of money to steam (before they added polish złoty they needed EUR, and paysafe cards do not divide evenly into euros)
Full Page Screen Capture - for capturing full page screen captures
Google search link fix - also just stolen
HTTP Headers - http headers
Night Messenger - dark mode for fb messenger, go @ me freetards
OWO - HEWWO? (yeah it's disabled (literally and figuratively), keeping it installed tho)
PDF Viewer - a in-browser pdf viewer which overrides automatically downloading PDFs, which the standard chromium pdf viewer doesn't do
Session Buddy - saves sessions, useful when i have to reboot my computer, and i usually keep upwards of 50 tabs open
Split Tabs - you can select a tab, and it splits the current window into two - the ones on the left and the right side of the current tab
The Great Suspender - an extension which unloads tabs after they are unused for some time, again i keep >50 tabs so it's useful
The QR Code Extension - creates a qr code with the current url, useful for quickly throwing an url to your phone
uBlock Origin - ad blocker

ive always wondered how honey makes money at all. They have to sell some user data. I just can't see any other way