The most beautiful thing I have seen are Mythic rare foil magic the gathering. That is because they are some of the rarest cards in the game having about 1/216 chance of getting one in a booster pack.
One reason why I think Mythic rare foils are the most beautiful thing is because if you get one in a booster pack you are almost never going to get another foil of that card unless you buy that online or in a card shop. Getting a mythic rare foil also makes you feel extremely happy by your card being shinier than other people versions of that card. For example in last may just a little while before I was going to be playing a game of Magic The Gathering I bought a booster pack and inside it was a mythic rare foil and for the rest of the night