And type of trimmer will be limited by how close it will get. But technically, by definition, a trimmer is not a shaver. It will result in a tight buzz cut. Some trimmers do cut so close that it may appear to be a head shave, unless looking closely. So most people will still think of it as a head shave.
Another consideration, if you hair is dark, and you have pale skin, the "shadow" left by a trimmer will be very pronounced. A true razor blade head shave will result in less of a shadow. Some electric shavers come close to a razor blade.
