If I were a billionaire, I think I’d just let tech sites and other blogs do my shopping for me. They find all the best stuff up for auction, and I’d just swoop in and buy them. For example:
A Tyrannosaurus Rex skeleton [Link]
A space shuttle [Link]
The “Ferrari” from Ferris Bueller’s Day Off [Link]
Cameron Frye’s house from Ferris Bueller’s Day Off [Link]
And of course, J.D. Salinger’s crapper [Link]