Sculptura - 3D sculpting for everyone
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
PaintCube - Web-based 3D painting software
Pixel Studio - The Pixel Art Is Always Fun
Nomad Sculpt - Nomad is a sculpting & painting mobile app, available on Android and iOS.
Piskel - Piskel is a website where designers online create sprites or pixel art.