I have been told that dinner at V&A's is SO worth it, but we haven't done it... yet...
Make a dinner reservation at California Grill and time it so you are there during Wishes. Magical viewing Wishes from the top of the Contemporary, with your sweetie and a glass of red wine!
Illuminations cruise. We've always just bought seats in someone else's boat, but next time I am going to try for a boat and then sell the seats to cover the cost. I LOVE Illuminations Cruises, and we haven't been able to get any seats for the past 5 or so trips.
NOT sure they are still doing this, but last October (2014) we stayed for the special after-hours tasting event at Epcot. We went to the tequila tasting in the Mexico pavilion. This starts AFTER park closing, so staying in the park is special in itself. There were about 25 people in attendance, in the tequila cave in Mexico. The host of the event was very knowledgable, and we were educated in the ways of tequila! The event was $35 per person, and it included 1 shot of vodka (to cleanse your palate), either 3 or 4 different tequila tastings, and an amuse bouche to go with each tequila taste. They also stayed open for a bit after the tasting, so you could order drinks and bar snacks (for an additional charge, of course). I thought the price for this event was reasonable, considering it's Disney, and we had an AMAZING time at the event!
Afternoon tea at the Grand Floridian. It's just so darned elegant, and when else will you get to experience a high English tea (kind-of)? We found that if we had a substantial breakfast and planned tea for about 3:30pm, we didn't need dinner; a park snack held us through until the next morning.