Rope.

Those suture-replacement bandages.

Superglue.

Memorize some songs, especially ones that work well in groups, such as rounds. They're good distraction when you get sick of playing cards, and unlike cards they work just as well in the dark. A small, tough musical instrument like a recorder or harmonica is also good to have around.

Caffeine pills come in handy if soda is unavailable or you can't boil water to make coffee or tea.