Pack a pen
Even if you’re not a budding novelist or a crossword fan, it’s a good idea to pack a pen with you in your hand luggage when you’re traveling. You might not need it, but if you find yourself having to fill in a visa form, or sign something at customs then you don’t want to be asking everyone on the plane to borrow one.
Filling in customs forms with your eyeliner pencil just isn’t considered very professional. If you’re stuck onboard with nothing to do for hours then perhaps you could start writing your life story, or at the very least do some doodling while you wait to disembark.