When we go to WDW without the kids we are lesser park warriors, so we do some different things. We enjoy a beer at the Victoria Falls lounge at AKV. We make the time to listen to the evening storytellling at the AKV firepit.
We sit in the lobby at VWL and look up. We rented bikes and rode over to Fort Wilderness for the buffet lunch at Trail's End. We rented the Sea Sprites (Water Mice) for a half hour (also do this with the kids) at VWL and zoomed all over Bay Lake, by Poly, the wedding pavilion, etc.
We take the time at Epcot to sit and watch the fountain shows (which DH loves). At MK, we went over to Tom Sawyer island on a gorgeous day when we were really tired and rocked in the rocking chairs for a most welcome and recuperative half hour rest. Then we raced over the barrel bridge several times because there was no one else there!
Though we don't always do something "new" each time, we try to rotate things we do so they stay fresh and fun!