Ublock Origin is an obvious one, but I also can’t stand not having Foxy Gestures anymore. It adds customizable mouse gestures, so you can set it up to have easy swipes to go back a page, reload a page, close a tab, etc, and it feels wonderful and smooth to use compared to just using the traditional buttons to do everything. Honestly it’s kinda wild to me that this isn’t more popular now that people are so used to phone gestures. It’s good for the same reasons!
I don’t use many extensions, but apart from the usual UBlock Origin I’ll say something exotic: UltraWideo
Because sites like disney+ still don’t know that 21:9 monitors exist so you have to force it to scale their 21:9 films to your monitor instead of giving you black bars on all sides