The Best Overall Winner is Thumbnail Zoom Plus!

Congratulations to the developer of Thumbnail Zoom Plus, David Adler! Read more about it in the announcement.

The Category Winners:

~ MOBILE (Firefox for Android) ~

Adds a translate button to the long-tap menu.

View and edit saved passwords on your phone, tablet or desktop.

~ MOBILE PORT (Firefox for Android) ~

Use your home button as you would in a desktop browser. Save from 1 to 4 links to open quickly with your new home button.

~ COMPLETE THEME (Desktop) ~

Smooth dark theme for Firefox.

~ UPDATED ADD-ON (Desktop) ~

Shows the full image when you hover over a thumbnail.