I have three, really.
The first was when I received my very first set as a child, an adorable little covered wagon set. I thought it was the most wonderful thing in the whole world. I don't think there's any way to describe how I felt at that moment.
The second was years later, after my years of being "too old" for toys were over, when I decided to see if playmobil was on the internet now!
Of course, it was, and I was so overwhelmed by how much it had expanded since I was a kid.
The third was when I saw the first pictures of the new safari sets with hyenas and ostriches. I literally couldn't breathe I was so excited. I almost fainted, I think! My husband was sitting where he couldn't see my computer screen, and he thought I was dying or something.