motion sickness tablets ( Bonine/dramamine etc)
beach towels/water shoes if hitting the water parks
MORE ziplock bags, for putting your socks in during water rides and whatever else you want to attempt to keep dry
extra card for digital camera...those things are big bucks in the parks!
if bringing an air mattress...remember your sheets and preferably not white like Mousekeeping's
the dishwashing cloths are long gone...I have about 10 left...only because I used to cut them in 1/2 when I took them on vacations. They are great, not sure WHY they are no longer made. I checked the camping stores too...no luck!
If you have your tix already, photo copy them and put the copies in your room safe. If the tix get lost or stolen, show the photocopies to guest services and they will take care of you.