Toggle animated GIFs lets you press Ctrl+M to enable/disable animation of GIFs in the current tab, and press Shift+M to restart all animations from the first frame.
Each large enough, non-background GIF also shows animation controls when hovered. If you find this too distracting, you can disable it in the addon settings.
There are also options for toggling GIF animations when clicked (for GIFs that aren't links, that is), and for disabling all animations by default (equivalent to the "image.animation_mode" about:config setting). You can also set GIFs to animate on hover, for use with the latter option.
Sample GIF for testing:
http://i.imgur.com/bGqUxUj.gif
Add-ons
