My laptop (I love doing offline things on the airplane like editing photos, videos, organizing)
A book (I started reading Sex, Drugs, and Cocoa Puffs by Chuck Klosterman... it's awesome so far).
A magazine (I range from wedding mags to fitness mags)
Chargers for everything that needs charging
Water & snack
Your makeup bag (because you never know how long you'll be at the airport and sometimes you need a fix-up)
An extra sweater in case the one you have on isn't enough
Moisturizer (something about airplanes makes me dry up)
Hand-Sani .. self explanatory.