Gosh there's lots in the DW parks that is great.
I'll separate by park:
Magic Kingdom:
Space Mountain, Mickey's Philharmagic

, Haunted Mansion , and Pirates of the Carribbean

, if you can also check out a night with Spectromagic parade going then stay for the Wishes fireworks.
Epcot:
Mission SPACE, World Showcase(any country, eat a great dinner here) , The Land boatride

, Living Seas

, Spaceship Earth(gotta see it at least once), Check out the Leave a Legacy sculpture(this is a monument made to showcase disney world fans)

, Ice Station

, the Future World dancing fountain, and of course the fireshow Illuminations
MGM:
Star Tours, Indiana Jones Stunt Show, Tower of Terror(not as scary as technilogically neat), The Great Movie Ride, The Muppets 4D(a total blast!)

, and Fantasmic is a must!!!!
Animal Kingdom:
This is a great park to just relax and stroll through

aw: , the kilaminjaro safari is a must, Kali River Rapids is fun on a hot day

, also check out dino USA, it's a fun themed area, Dinosaur is kinda fun too

.
Other:
Cirque du Soleil! Awsome and Amazing show at Downtown Disney, DisneyQuest, a 5 floor arcade and VR Arena for technogeeks of all ages or just people who like to play video games(Try the neat buzz Lightyear tank game or the drawing/animation machines)