Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
MagicaVoxel - A free lightweight GPU-based voxel art editor and interactive path tracing renderer.
Pixel Studio - The Pixel Art Is Always Fun
Goxel - Goxel is a simple, but powerful voxel graphic editor with 24-bit color support, unlimited scene...
Piskel - Piskel is a website where designers online create sprites or pixel art.
Cubik Studio - Model in a unique cubic style. Start modelization with boxes. Move, rotate and scale cuboids.