Terragen - Terragen is a scenery generator, created with the goal of generating photorealistic landscape...
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
World Machine - Command powerful tools like erosion and advanced colormaps to create terrain heightmaps, meshes, and textures for your game or 3D scene. Download for Free!
Pixel Studio - The Pixel Art Is Always Fun
MagicaVoxel - A free lightweight GPU-based voxel art editor and interactive path tracing renderer.
Pixel Art to CSS - Draw and animate pixel art, export the results to CSS