One additional item that I wished I had on my cruise last week that wasn't on any list is an extension cord. I need a sleep apnea machine to sleep. The one plug was on the opposite end of the room from the head of the bed. Luckily, between the length of the cord for the apnea machine and the length of the air hose, it was just about long enough for me to lay in the bed normally w/o having to reverse directions.
Another option would have been to rearrange the direction of the bed within the room.
If you are the type that need special machines to sleep, you might want to consider a 6 feet extension cord.