I'm not one to rate pins as being on a certain list, A, B, C. I personally rate them as fun to me or not. I don't buy a pin, or seek on out because it's an "A" list pin.
I notice a lot of people referring to getting an "A" list pin in their collection.
There is no defined list.
In your own words, what makes a pin an A list pin? Price, rarity, design team, difficulty to play? I want to hear your personal opinion, not the canned version. I personally, do put pins on lists, unless it's a list to buy or sell.
I know, it's been discussed before, a million times.