There are two words which are used exclusively as names for Allah. No one else may be called by these names under any circumstances, regardless of the context or grammatical usage, and regardless of whether the words are being used as names or descriptions.
They are the name "Allah" itself and the name "al-Rahmân" (the Beneficent).
Allah says: "Say: Call upon Allah or call upon the Beneficent, by whatever name you call upon Him, (it is well): for to Him belong the Most Beautiful Names." [Sûrah al-Isrâ': 110]
This is why no created being is ever called by these two names except that Allah has brought that person to disgrace. One of these people was Musaylimah, the false prophet who called himself "al-Rahmân." Allah brought death to him, ignominy, and disgrace to his memory. His followers used to call him "Rahmân of the Yamâmah region", Allah punished him with the evil reputation that he acquired during his lifetime and that persists with him throughout history.
The rest of the words which are mentioned as names for Allah might possibly be used to describe others as well, in one way or another; for instance: "Seeing" and "Hearing". Allah says: "Indeed we created the human being from a mixed drop of fluid to test him, so we have made him hearing, seeing." [Sûrah al-Insân: 2]
The same can be said for gentle, merciful, lofty, great, well-acquainted, and the other words which are used as names for Allah. However, there is a great difference in the connotation of these words when used to describe Allah and others – the difference between Creator and creation. The reality and attributes of the human being are in conformity with the nature of a created being. Therefore, when a person is described as possessing the gifts of "hearing" or "seeing", a modality of hearing or sight is intended with all of the limitations that the human senses are constrained by. There are limits to perception that human beings will never be able to transcend.
By contrast, the attributes of our Lord have a totality, a limitless perfection, that our minds cannot even begin to fathom. Our inability to attain a true realization of these attributes is in itself a form of realization for us.
It is possible for a created being to be described with he same word that is also used as one of Allah's names, but there is an immense gulf when it comes to the reality of what the word describes when it is used for Allah and when it is used for a created being.
And Allah knows best.