You do not have to worry much about being a copycat if you do not find the most unique cover letter format in town. Just be sure that the contents of the letter have a clear and definite direction. This will bring about a good flow in the contents of the letter.
Of course, you will eventually realize that even if you do not get that frenzy over the cover letter format, you will still have to pick one template to start on among many choices. Thus, it pays to know some essential points that will help in making a good cover letter.