Electric Zine Maker
art tool for making, formatting, and printing zines, has some bugs and is still being developed but it's fairly useful
LÖVE
2D game engine
LibreSprite
program for making/animating pixel sprites
Paint.NET
image and photo editing software
Decker
engine for making things like interactable images, games, visual novels, and more
LibreOffice
office suite style software, open source, focus on free access
Krita
art program for digital illustrations and animation
ink
scripting language for making games
GIMP
image editor, photo manipulation, art program, graphic design
GB Studio
drag and drop game creator for making game boy games
Blender
engine for making 3D animation, modeling, art, etc
Audacity
audio editor and recorder
Godot Engine
engine for making video games
Ren'Py
engine for making visual novels and games
OpenShot Video Editor
video editor