The following is a personal rant about a personal pet peeve. I don't know how adcoms feel about this, just how I do.
If you're really thanking them, why not use custom hand-written thank you notes? Almost nobody does it, but when someone gets a thank you note that really looks authentic and is really customized, it helps. Strangely, when I student host, I never get a thank you card, a gift, and rarely do I even get help cleaning up after the applicant. This btw, takes wayyyy more time out of my schedule than interviewing. Meanwhile, the people I interviewed on the MD side always sent me canned, obviously repeated, printed thank you notes. It's obvious that it's just a fake little gesture. I wish I could deduct points for all those letters that were obviously just copies of letters sent to others. "Thanks for interviewing me, now let me spend the rest of this page telling you why you should accept me." Ugh, makes my blood boil with the fakeness.