The Pledge

• A pledge close can be a good way for the letter writer to bond with the recipient in meaningful ways. Such closings can provide a sense of the dramatic and reflect common backgrounds, or relatable challenges or triumphs. Closings such as "yours in adversity" or "yours in victory" may work well.
  
  

The Unfinished Sentence

• Sometimes an incomplete sentence that can only be completed with your signature has a nice effect. In this way your name ends the letter, as well as being its close. An example might be, I am glad you accept a variety of people into your club as I can only be . . . your name or signature. Such a closing is clever and humorous as well.
  
  

The Verbal Flourish

• The idea of the verbal flourish is to be literary, original or humorous. According to everydaycorrespondence.com, some closings that might work well to accomplish this are the old curse propagated by the Chinese, "May you live in interesting times" and even the theatrical "Exit stage right."
  
  The recipient will certainly remember such closings when thinking of the letter.
  
  

Avoid Sincerely

• To be clever in closing requires avoidance of the mundane and overused. Sincerely is used in so many letters it is doubtful to garnish any worthwhile reaction. Stay original and reflect your purpose for writing the letter instead. Use "Sympathetically" for condolence letters and "Inspirationally" for a letter to a friend to lift his spirits.