Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
ezgif.com - Ezgif.com is simple online gif maker and toolset for basic animated gif editing.
Pixel Studio - The Pixel Art Is Always Fun
Instagiffer - Create GIFs from anything!
Piskel - Piskel is a website where designers online create sprites or pixel art.
Gifsicle - Gifsicle is a powerful, simple command line tool for creating, editing, and optimizing animated GIFs.