The largest galaxies are the giant elliptical galaxies. They may be 20 times as large as normal galaxies, and are often located in the centers of clusters of galaxies. But the dwarf ellipticals are by far the most common type of galaxy. When we look at any region of space with longer and longer exposures to see fainter and fainter objects, we always see more and more dwarf ellipticals. It's not actually clear if there is a lower limit to their size.
Lenticular galaxies are sort of a cross between ellipticals and spirals.
They have a bulge and a disk, but no spiral arms, and no interstellar medium or young stars. Galaxies which don't fit any of the above are called irregular. There are two main types. The Irr II are very distorted, with appearances which often suggest that some kind of collision or violence has occurred.