What is it about [ENTITY REPRESENTED BY INTERVIEWER] that brings you here specifically?
Keep in mind that the interviewer has the advantage--he or she can hire someone else easily enough--so this is your chance to not just say why you'd be good for the organization, but why it would be good for you, too. It sets a motif of your being on the 'same page,' and people sharing the same page fit well together. The linchpin of this strategy is their 'Mission Statement' or 'Vision,' which are one or both prominently displayed on their website landing page. These are usually very short and generic, but professing paraphrases from them can be used to show you 'get it.'
You can tell the interviewer that their values align with your personal values and that's important in your plan for the rest of your professional life. (Don't actually cite their 'Mission Statement' and 'Vision,' but state that you find this group's values align with yours.)
"I know that I have found a place here where the values align with my own. I've really done a lot of research and I especially like your dedication to community interaction, your embracing diversity, and always putting the patient and his or her family first. I think I'd be very happy here with the professional mindset and I'd be a good fit."
