Dramamine (for motion sickness or nausea in general) Sometimes one too many rides on BTM makes me a little dizzy. These are a lifesaver. I always take one before getting on a motion simulator such as Star Tours. Also a lifesaver after eating something that doesn't sit well with you.
Rolaids/Tums, etc... (often needed after a few days of eating at WDW)
sanitary napkins (I didn't expect that to happen on my last trip and didn't bring any)
Tape and scissors (great for sealing up opened shampoo bottles for packing.
Bubble wrap...(Yeah I know it sounds crazy but when you buy delicate souvenirs it protects them nicely. Also great for keeping pins from scratching against each other.
Zip Lock bags to seperate dirty undies, socks, etc from clean clothing...
Extra Batteries for Walkie Talkies, digital cameras, etc...
A couple of paper plates. When we get take out at the Contemporary's Food And Fun Center we often share. I bring a couple of plates to divide up whatever we bring back.
Earplugs. Got a family member that snores? Definitely bring these!
Address Book. In case of an emergency for contacts.
I always carry a small container of pills (tylenol, antacid, gravol, etc...) so if I don't feel well I can remedy the situation right away instead of heading back to the room.
Travel Wipes. For sticky/dirty hands when a sink is not in the vicinity
Eye Glass Wipes. The heat and humidity can make for some dirty lenses. Anti-fog glass wipes are a snap for a quick clean up.