These are my favorite and most used extensions used with Chromium in Gnome.

DuckDuckGo Privacy Essentials - Chrome Web Store

Accessibility Developer Tools - Chrome Web Store
Accessibility audit and element properties.
This extension will add an Accessibility audit, and an Accessibility sidebar pane in the Elements tab, to your Chrome Developer Tools.
Copy as Markdown
Copy Link or Image as Markdown code
Adblock Plus
La herramienta gratuita para bloquear publicidad en Chrome: anuncios en vídeos de YouTube y en Facebook, banners, y mucho más.
Google Analytics Opt-out Add-on (by Google)
Tells the Google Analytics JavaScript not to send information to Google Analytics.
Responsive Inspector
Responsive Inspector allows inspecting page media queries. LiveReload
Provides Chrome browser integration for the official LiveReload apps (Mac & Windows) and third-parties like guard-livereload and yeoman.
Page Ruler
Dibuja una regla para obtener las dimensiones en píxeles. Mide objetos de cualquier página web.
Screen Capture (by Google)
Capture visible content of a tab, a region of a web page, or the whole page as a PNG image.
Tape
Measurement tools, rulers and grids
Ripple Emulator (Beta)

A browser based html5 mobile application development and testing tool
Chrome Web Store - WhatFont
The easiest way to identify fonts on web pages.