Although, cover letter adds to the wear and tear of job search, yet it gives you another chance to emphasize what you have to contribute to the company or Organization. Hey! Do not give the recruiter a second to entertain thoughts like: But how can this person help us? Though your resume can answer this question, it does so in a ‘rigid’ format. Whereas, the cover letter allows you to answer in your own words and style.

Your cover letter should contain not only your experience; it should also show how and what you can contribute towards the positive growth of the firm.
Example:
Weak: I have good knowledge of web programming and Application development.
Better: Due to my strong knowledge of web programming and Application Development, I will develop a better structured standard compliant, information system infrastructure which will make processing easier thereby saving work time and money.
The cover letter is the only place you can add what you can do for the firm (not just what you can do); exploit it!
Except where it is otherwise mentioned all applications should be submitted with a well written cover letter.

^^^ Nice one Mate!