Thanks for the response, but I guess that's what I consider sounding a little trite and obvious. Thanking the interviewer for his/her time goes without saying, and you know that you will hear back from them - even if it's a waitlist/rejection letter. I guess I'm trying to come up with something that has a little more punch - something that leaves a favorable final impression in the interviewer's mind.
Would it be inappropriate to give a kind of a verbal letter of intent? For example, "ABC is my number one choice for med school - this is where I want to spend the next four years." Or should I save that line for a written letter of intent?