firegestures,imagus,stylus,better-youtube-subs then finally “Dark background and light text”.
Firegestures || Mouse gestures and mouse gesture events/macros
Imagus || Enlarge thumbnails, and show images/videos from links with a mouse hover.
Sytlus || Stylus allows you to easily install themes and skins for many popular sites.
|| allow you to mark video on your subscription so you hide them or any videos you have watched get hidden.
Dark Background and Light Text ||
Makes every page to have light text on dark background (exact colors are customizable )