3D Pixel Artist is an app that helps you design voxel arts. It's very intuitive and easy to use. Your designs can be 3D printed too! It supports exporting to STL & OBJ models.
• Draw Mode to add voxels
• Paint Mode to change the color of the voxels easily
• Move Mode to move a group of voxels
• Delete Mode to delete voxels
• Mirror Mode to add voxels symmetrically
• Support 3D printing of your designs, in full color or monochrome
• Support exporting to STL and OBJ file formats