Game Boy filter for your images.
Open-source painting software that even works on Linux.
My past (when I still used Windows...) go-to image editor. Supports plug-ins and whatnot.
Faithful recreation of Windows 95/98's MS Paint in-browser. Lets you export a process as a gif.
Lots and lots of older smiley emotes. Love those.
Practice the fundies with free Loomis.