The Postscript Technique
If you want to add an extra splash to your cover letter, consider adding a P.S. at the end. This works especially well in focusing on your most marketable attribute. An example would be:
P.S. I was the first intern ever to receive the Employee of the Month award at Ernst & Youngs New York office. And I won it not once, but twice. I am looking forward to bringing that same level of passion for my work to you at Big Public Accounting.
And if you truly want maximum impact, handwrite your P.S. I guarantee it will be the first thing read.