Crown Jewels in your Collection

While most of us collectors cherish what we have, there's always one standout item that could be considered a crown jewel because of its rarity, price or personal attachment. 

What do you consider to be your 'Crown jewel'? For me it would have to be my bluray edition of the anime Wakako-Zake. While yes it's slightly obscure, it isn't all too rare or that expensive but I consider it to be my crown jewel because I heavily enjoy it.