Unity - The multiplatform game creation tools for everyone.
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Pixel Art to CSS - Draw and animate pixel art, export the results to CSS
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Piskel - Piskel is a website where designers online create sprites or pixel art.