Despite what
DCL says (i.e. "no irons,") I'm glad we brought along our little travel iron. No, it didn't blow out any circuits, and having it made life a lot easier (never stood in line for that beaten up old thing in the laundry room, the portable worked fine on the coffee table with a towel thrown over it.)
Those recommending a night light for the bathroom are correct, although we found (with a veranda cabin) leaving the curtain open just a wee bit at night provided just enough light for anyone getting up in the dark, plus it let that wonderful Caribbean sun in at morning which was a great wake up call.
We also brought along an extension cord but never used it. My wife said the installed blow dryer in the bathroom was "adequate," but in retrospect she wished she'd brought her own along (I sense this is a highly subjective thing).
We brought along our two way radios, and used them occasionally (during the ressie scramble -- which turned out to be a non-event on our cruise - as well as when grabbing spaces near the front of the line to disembark while at ports).
Like someone else here, I found space in our bags to stuff a small plastic pail and two shovels for our kids. Everyone at Hawksnest Bay in St. John and at
Castaway Cay kept asking us "where did you get those?", to which I responded "at the KMart in Manhattan."
I also HIGHLY recommend a waterproof bag to keep your valuables in (money, cameras, camcorders, etc.) when on shore excursions to the beach or on boats, as well as while you are up at the pools on deck 9 (I could romp in the Goofy pool with my kids and not worry about our stuff getting snatched, which unfortunately does happen even on DCL). Mine is a splashcaddy (
http://www.splashcaddy.com).