a milk
A super rare thing you can only get after 15 years of waiting. It's like trying to get a rare Pokémon but with more waiting and less excitement.
I've been waiting for it since 2008, and I still haven't gotten it.
It took my uncle 20 years to get it, and he still hasn't used it yet.
My cousin waited 15 years just to get it, and it was just a little milk.