Accomplishments can be processes or procedures that you have streamlined and made more efficient. Time saved is money saved for the company. Perhaps feedback from a survey on your performance or interaction with customers has been extremely positive. This is gold to a company as the happier the customer the greater chance of repeat business and new business. Then there are awards or recognitions you may have received. These would also count as accomplishments. In addition, accomplishments do not have to be an individual effort but rather it can be part of a team project that significantly impacted the company such as a relocation, new technology implementation or assisting during a reorganization.
Many times we do not even realize how important the job we perform can be to the success of a company. If you are really stuck then I would suggest asking someone that is close to you. They usually can see your accomplishments clearly. Or just take some time to think it over and write down what you have done over the course of your career that you are proud to have achieved.
Also, do not be afraid to talk about yourself as you are not being egotistical. These are your accomplishments and you should be proud of every one.
Hope this helps! As always feedback is appreciated! Sue