uBlock Origin is always the obvious answer.
SponsorBlock for YouTube.
FastForward to skip the delay on link shorteners.
Reverse Image Search does what it says.
Imagus enlarges any image you hover over with your mouse and saves you clicks, but can get in the way sometimes.
Flag Cookies has a lot of uses, but it’s mostly there to just grab my Google Drive cookies so I can download things a lot more efficiently with jdownloader2.
Recipe Filter if you’re trying to cook something but don’t want the writer’s autobiography.
ColorZilla if for whatever reason you want to steal the exact color code of a thing in your browser.