The plane ticket thread, coupled with the fact that I'm in the middle of packing for our trip next week, just made me wonder: What things do you always need in your carry-on?
For me, it's a good book, my iPod and giant DJ headphones (so people can see that they shouldn't try to talk to me. I'm anti-social), red licorice (no idea why; this goes back to when I was a kid), pain killers (just in case), and my neck pillow if it's an international flight.
I usually have a bunch of other random stuff too; sudoku puzzles, a magazine, other random snacks, etc. But those are my must-haves. What do you bring?