Nearly everyone starts their cover letter with something like, I am writing in response to your job opening, blah, blah, blah. (ejobapplications.com)
Always start your cover letter by putting your name and contact information in a block in the upper left corner. (cvtips.com)
Thinking of starting your cover letter for gift shop manager something like: «Please accept this application letter in response to...»? (coverlettersandresume.com)