RKMBs Forums .::Robegories::. Comic Books What's the Holy Grail of your comics collection?

I actually thought of two ways to answer this.

What series or issues or other items do you treasure the most in your collection?

Or alternately and at least as interesting, what items did you struggle most to find and purchase to add to your collection? What are the rarest and hardest to find items you have?
What item did you search years for, and maybe not yet found?