Ok but heavy handed approach Rated 3 out of 5 stars
It works by completely removing all .gif images so they can't load but it also blocks useful non-animating type gifs on some sites, like dictionary sites (merriam-webster, tfd), that use gifs to show the audio icon or pronunciation key.
A better approach would be to load the gif images and then stop any gifs that are animating. Or offer it as a separate option. I know pressing the Esc key stops any animating gifs. Maybe you could have this addon automatically press the Esc key after the page is done loading or something.