We recommend talking to your coworkers and family to ask them what your one unique thing is. You may be surprised at the consistency in their responses, and it will give you great insight into how to answer this question. Perhaps you can mention that your prior experience in working with a large and growing company has allowed you the breadth of experience necessary to be an effective Technical Support Specialist. You may mention that you are frequently praised for your ability to be an articulate and effective communicator, or you may discuss how you have a knack for analyzing tech-related problems.