Hey Opponauts! I need your help and ideas. Recently I took a new job that is going to require a hefty amount of travel - my first job like this. I'm a pretty good traveler for short trips around the country, but this is going to be a lot of day trips and train rides and maybe some hotel stay. So here's my question to you seasoned job-traveling veterans:

What can't you live without while traveling and what does your daily bag look like (Clothes, gadgets, apps, etc)? Hell, what IS your daily bag?

I know I could ask LifeHacker or Giz this, but I trust our ilk more, and want to know what you carry. I basically always carry an external battery for electronics, a streaming media flash drive for when I'm out of cell reception but sitting on a train, headphones, one extra day of clothes (if multiple days of trip), a book and work files, laptop and whatever else might be required by the trip - how about you guys?