I always carry a copy of my printed AMCAS, a copy of the secondary for the particular school, my transcripts (official or student copy), a checkbook (incase I am able to bribe someone), my resume, and a magazine to read/kill time with.
Breath mints! I interview a lot of people in my current career, and have seen many a firm handshake totally tubed by stanky breath. This goes doubly if you're likely to get so nervous that you barf beforehand😱
A safety pin is also a good idea - there's nothing quite like having your confidence destroyed by losing a button on your shirt 5 minutes after you reach the school. Lots of nervous chair fidgeting ensues.