The least common shape for a galaxy is cluster. Galaxy, by definition, is an arrangement composing of stars, planets, gasses and everything more that can be seen in the space. There are three types of galaxies and they are elliptical, spiral and irregular. Spherical could be applicable as elliptical if you got to choose only one on the choices above. Example of spiral galaxy is the Milky Way galaxy where our Solar system is currently located according to the scientists. The considered satellite for Milky Way is letter D: Copernican Dwarf Elliptical or Sagittarius Copernican Dwarf Elliptical.