MoviePy is a Python library for video editing: cutting, concatenations, title insertions, video compositing (a.k.a. non-linear editing), video processing, and creation of custom effects. Use it to convert videos, make animated gifs, add effects....
Piskel is an online, opensource (https://github.com/juliandescottes/piskel) pixel art and animated game sprite editor in the 8bit style. By manipulating discrete pixels in your web browser you can draw and animate c64 and nintendo style sprites, preview the animation, export them to animated gif files, and download them to incorporate into your own games.