Piskel - pixel art and animation online tool
If you are into pixel art then this online tool solves most of your issues ... and it's free!
It supports layers, it has a nice tools to help you out with sprite animation and creating tiles. It's simple and always available. Perfect for game jams and small projects.
Link: https://www.piskelapp.com/
Portable Apps
Launcher and Maintainer of over 1400 free and mostly open source applications. It contains portable versions of well known programs like Blender or GIMP plus many more that you never thought you could find useful until you saw them in the list of apps. What makes me stick to this platform for over a decade is that it takes off the responsiblity to worry about updates for those apps. This has functionality of linux GUI package managers but it is for windows.