My packing list for any length cruise includes these documents, in order of importance:
State ID, passport, and copy of passport
Boarding passes for flights if I have to fly
Copies of prescriptions for all medications
Confirmation emails for tours, hotels, etc.
City maps for all ports and ship deck plan
Of course, all of that belongs in my carryon, not the bag I will check. While shopping in February for a new set of luggage bags one criterion was a large front pocket an 8.5x11 sheet of paper can fit in unfolded because I keep all travel documents in a folder except the actual state ID and passport.
The larger bag I check will always contain:
White mesh laundry bag with zipper
Extra walking shoes in case it rains
Lightweight rain jacket (not plastic)
Waterproof sunscreen (over 30 SPF)
Very loud portable travel alarm clock
My younger sister thinks hotel-provided hair dryers are never good enough so she likes to pack hers. But I never use them and see no reason to worry about the wattage. Now packing her curling iron makes a lot more sense because hotels don't offer them, but of course that is only if you look terrible with straight hair.