Translate Web Pages - translates entire pages into your language, can do it automatically. Google Chrome may have this feature built-in but other Chromium browsers don’t.
Consent-O-Matic, automatically fills out cookie banners for you (e.g, it’ll auto deny all cookies). This is better than just hiding or ignoring the cookie banner. It doesn’t work on every cookie banner though.
Decentraleyes - “Protects you against tracking through “free”, centralised, content delivery. It prevents a lot of requests from reaching networks like Google Hosted Libraries, and serves local files to keep sites from breaking. Complements regular content blockers.”
uBlock Origin - with the right filters, this will catch almost any ads, trackers, and help protect you from malware while browsing the web.
Some bonus ones that aren’t really essential but nice to have:
Imagus - Enlarge thumbnails, and show images/videos from links with a mouse hover.
IBA Opt-out - Opt out of Google’s interest-based ads as you browse the web with Chrome.
Reddit Enhancement Suite - if you still use old.reddit, this will improve your experience significantly.
SponsorBlock - auto skip sponsors in YouTube videos, and other useless content.
Stopaganda Plus - displays a bias rating from mediabiasfactcheck.com for countless news outlets. Understanding the biases of news outlets is essential to understanding their point-of-view.
Web Archives - view archived versions of pages. Particularly useful if you ever come across a link that has since died.
Some bonus ones that aren’t really essential but nice to have: