If you're a reader and like to read while on vacation, plan on having some time to do this. A deck of cards, checkers, or a backgammon set can be fun to have around in the evenings. Certainly during the trip they can help break up the monotony of driving. Towels are available for rent at the water parks, but they're small and it's a pain to have to pay for them. I like to have a pair of water socks, too.
Some people love 'em, some people hate 'em.
Take 'em if you love 'em. A travel alarm clock. Besides, I use the travel alarm at home, so the noise that it makes is familiar to us and wakes us up without a problem. Change for Florida's toll roads. There aren't a lot of them, but they can be a pain if you have to break bills to pay each time.