Blender - Blender is the open source, cross platform suite of tools for 3D creation.
MagicaVoxel - A free lightweight GPU-based voxel art editor and interactive path tracing renderer.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Cubik Studio - Model in a unique cubic style. Start modelization with boxes. Move, rotate and scale cuboids.
Sketchfab - Sketchfab is an industrial design software tool is useful for ideation and for beginners in the industrial design field.
Voxel Builder - Design and edit 3D voxel models in your browser.