"It Belongs In A Museum": Spielberg reveals that he owns the Rosebud sled from Citizen Kane. Is this the greatest movie memento ever? How can anyone beat that?

Dorothy’s ruby slippers? I don't think there is any other more cherished memento. Supposedly, Peter Jackson owns the boat used in "Titanic," where do you put it for safe keeping? private beachfront? 

The MGM lion, stuffed. Which was originally owned by Ted Turner. He kept it at CNN in his office. You could see it through his window.

There is a famous story about Steven Spielberg and Orson Welles, one that has been repeated so often that it is perhaps better to assume that the details are all wrong. But the story holds that Welles had asked Spielberg and his then-wife, Amy Irving, to dinner. Ostensibly, Welles was to interview Irving for a part in his latest film — a film that would never be made.
But Welles was alert to the fact that this was Steven Spielberg, and that Spielberg was a fan. Spielberg had bought at auction Welles’ shooting script for Citizen Kane; he had spent some $55,000 to acquire one of the Rosebud sleds used in the movie (presumably not the one we see burned at the end). Welles was hoping Spielberg would give him money.
But Spielberg didn’t volunteer and Welles was finally required to ask. And Spielberg said “no.” And then the check came. And Spielberg — whose Indiana Jones and the Temple of Doom was at that moment earning about $10 million a day — did not reach for the check.
The story may not be true, but it makes a good story.
This is from a 1985 New York Times article about Wells, and is probably what actually happened:
After the collapse of the ''Cradle'' project, Welles met the director and producer Steven Spielberg for the first time and found himself in a familiar and painful predicament - talking about his illustrious past when it was his new projects he longed to discuss. As a disappointed Welles reported afterward, he appreciated Spielberg's attempts to help, but ''we spoke almost entirely in the past tense at dinner.''