We just returned from the Carnival Victory to Cozumel, Cayman and Jamaica. We found excellent advice from this site on what not to forget

1) duct tape- our zipper broke on our clothing bag on way home.(2) power outlet- only one outlet in room, needed to plug in batt charger for camera and clock (3) small alarm clock- know what time it is- alarm for short naps or (for me) get up at five and watch the sun rise up on deck (4) those little walkie talkies- to keep in touch with my three teens! (5) a small sewing kit- daughters button came of her skirt (6) your own hair dryer- the one in the room barely worked
I think thats it..... or........