Most people cant function without their cell phones. And cell phones are high up on the food chain of vulnerability as far as what technology is needed for them to work.
The people hooked on texting would suffer terrible withdrawal.
Besides the obvious things to have on hand, books would be very important.
Ya. But even doing simple math will be difficult for many. The schools put a lot of emphasis on calculators these days and few young people can do long division or even multiplication.