From my parental perspective: Food and rest. My kiddos get unreasonably cranky when they're hungry, especially if they're tired, and vica-versa. It makes everything infinitely more difficult. Sleep, meals and snacks save my sanity on a good day. LOL!

EDIT: Boredom sucks incredibly bad too. I give them jobs/responsibilities, entertainment and free-time to combat that, so they'd likely be important in a survival or emergency situation too.