(and a pretty necklace that benefits anti-human trafficking orgs, and a pink clay face mask, and a Turkishtowelscarf, and a macrame plant hanger, and purdy nail polishes, and a really lovely folio clutch thingie...)
I saw someone else already linked the trtl neck pillow! mine helps a lot with neck pain. I also use an eye mask so I can sleep even when lights change around me. I also usually pack a turkishtowel as a blanket / scarf / backup towel. they dry really fast!