What was the hardest thing in your collection to find?

Not the most expensive item in the collection, but the one you had the most trouble seeking out.

For me it would be the PAL version of Mega Man 7 for the SNES. At the time of writing this, I see only three loose cartridges on EBay, all of which come from different countries, including Australia. It is to date, the only PAL copy of a game that I had to import because of the lack of stock in my home country.