I have been to WDW three times as an adult, and these are the attractions I haven't ridden/shows I haven't seen...
-MK: Tom Sawyer Island, Dumbo, the Tea Cups, the Carrousel, Ariel's Grotto, all of Toontown except Minnie's House, Tomorrowland Indy Speedway, Astro Orbiter, Timekeeper (and sadly, never will)
-Epcot: Turtle Talk with Crush (a big priority for this year's trip)
-MGM: Playhouse Disney, Honey I Shrunk the Kids Movie Set
-Animal Kingdom: Pocahontas and Her Forest Friends, Character Greeting Trails, Everest (this will be rectified in July

)
We've never stayed at any resort other than a value resort (once at ASMu, twice at POP.) Never even set foot in a moderate resort.
We haven't been to the Grand Floridian, Wilderness Lodge, or any of the Epcot area resorts.
We haven't done the Hoop De Doo or Polynesian Luau.
We've never been to Blizzard Beach, the Wide World of Sports, DisneyQuest, or any of the miniature golf courses.
We haven't seen Cirque Du Soleil.
We've never been to any of the special holiday stuff, like
MNSSHP,
MVMCP, the Candlelight Processional, etc.
We've never ridden the ferry to the Magic Kingdom.
We haven't done any guided tours.