Giphy - Search all the gifs and make your own animated gif
Enhancer for YouTube - Tons of features to improve your user experience on YouTube™!
GIFmaker - GIFmaker gives you the freedom and flexibility to create unique, professional GIFS that are on-brand, on your own!
ImprovedTube - Allows you to improve and enhance Youtube visually or enable dozens of new features permanently or...
GIPHY Says - Turn your words into animated GIFs!
Iridium by ParticleCore - Iridium is an extension built to improve the user experience on the new YouTube Material layout.