On our last day, we always hit all 4 parks, doing our favorite attraction "one more time" in each one.
When we leave MK for the last time, we always turn around and wave at the exit stiles and say "Goodbye Mickey!" and say when we'll be back (we usually know the next trip dates, but if not, just say "next year")
We eat at CP at least once a year, and measure how much dd has grown by how many stripes she comes up on Tigger.
We keep a journal each night back at the hotel, describing the funniest moment, the most magical moment, and one thing new and one thing revisited each day.