If you asked random people what is the most dreaded interview question to answer, chances are a majority would respond in kind with the same response - What is your greatest weakness? Everyone knows it's coming, but not many people know how to answer this appropriately or in a way that will be positive to the interviewer. Let's start with the answer that will definitely paint you negatively to the interviewer:
I Have No Weaknesses.
Okay, really? Maybe you don't see them as weaknesses, but everyone has a professional area where they could use improvement or development. The person interviewing you also knows this. By answering the question this way, you are presenting yourself as someone who either did not give the interview any forethought or as someone who views themselves as a professional who neither desires nor has room for growth. This is the last trait a hiring manager wants to see. They want to know you are eager to learn and develop your current skills and abilities. A candidate who is excited to branch out, expand and strengthen their talents is a candidate who is more likely to be hired.
Something else to consider: when you do decide on an area of development, or weakness, be cognizant on how your answer. You don't want to sabotage yourself by giving a weakness that is going to send the interviewer running for the hills (i.e. I can never be on time! I always take too much time off.) Maybe you have a difficult time delegating projects to others. Or maybe your perfectionism keeps you from maintaining a steady workflow. (Also, be careful with using "I'm a perfectionist" as your answer, this can also suggest a lack of forethought to the question.) Whatever the case may be, you need to frame them in a way that includes your plan to better develop and improve on these areas.
You're not being asked this question because the interviewer needs to know if you suck at multitasking or using Excel. They want to see how you respond, how self aware and willing you are to develop and strengthen your professional capabilities. Really they just want to see someone who is willing to put in the effort and energy to better themselves and consequently, the company they would work for.
Simply take some time, think about areas you could improve on. Think of projects that made you feel uncomfortable or out of your comfort zone. What abilities do you struggle with on a day-to-day basis? These are the areas you could bring up as areas of development.
A great follow up to this question, (remember, an interview is a conversation between two people deciding if both of you will be a good fit for each other) would be to ask how the company or department facilitates development and training in their team members. An experienced interviewer or hiring manager will appreciate a question like this.