The two purchases that really transformed Disney for me were a small, light, portable charger so we would never have to worry about running our phones down using Wi-Fi in the parks, and a sports band for my eyeglasses so I could finally just leave them on no matter what I rode. Having dropped my eyeglasses out of my parks bag without realizing it in the unloading zone of Space Mountain at 2am before, the latter is probably more significant than the former for me. Having your broken eyeglasses handed to you by a cast member at 2:10 in the morning, then having to grope your way through a psychedelically illuminated Magic Kingdom back to the bus stop is something I only ever want to have to do that one time.