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.