Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Union Bytes Painter - 2D sprite and low res texturing tool for editing with color, normal, height, roughness, and metallic maps.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Zero Brush - blendersensei.com/zero-brush Texture painting, sculpting, and baking addon for Blender.
Misfit Model 3D - Misfit Model 3D is a 3D model editor that basically operates with triangle-based models.
ShapeShop - ShapeShop is an advanced and professional 3D design and modeling application that comes with an easy-to-use and user-friendly interface.