Do something you have never done before.
sports: golf, mini-golf, fishing, RPDE, marathon, bowling, ESPN Club, WWS/ESPN Zone, etc
shopping: DTD, area outlet malls, large scale malls
drinking: Jellyrolls, Raglan Road, monorail tour of resorts, walking tour of resorts in the Boardwalk area
movies: DTD 24 screen theater some with meals served by waiters
night clubbing: Jellyrolls, Atlantic Dance, Raglan Road, Citywalk
resort tours: monorail tour of resorts, Boardwalk around the lake tour of resorts, AKL/AKV
offsite: Gaylord Palms Resort, Citywalk, swamp tour
Take the time for yourself and enjoy.
Depending on your situtaion, you may want to do the adult things that the kids do not allow or if no kids, always do adult things, then go be a kid for the day.