Unity - The multiplatform game creation tools for everyone.
Scratch - Scratch is the programming language & online community where young people create stories, games, & animations.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Tux Paint - Tux Paint is a free, award-winning drawing program for children ages 3 to 12 (for example, preschool and K-6).
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
GCompris - Educational Game for Children 2 to 10 years old.