My Top 3:
An E-ticket attraction - Anybody want to take a guess on what the last one of those in the park is? Splash Mountain, folks. Sure the New Tomorrowland rehab was more than just an E-ticket, but most of what was great about that is gone. 1992 is the last time this park got an E-ticket attraction. Unacceptable.
An attraction NOT based on a pre-existing character - Note to management, remember back when some attractions could be considered completely original? Remember when the Magic Kingdom was more geared towards families and not children? It can happen again.
A good table service restaurant that isn't a character buffet - We're going to WDW in June for 9 days. We have ONE ADR for the Magic Kingdom (Liberty Tree Tavern at lunch). That's right ONE. The Crystal Palace is good, but they decided to add a $4 summer surcharge this season. If Tony's Town Square had a decent menu with decent prices, it could easily fill this void.