There's a bunch of secrets in Legend of Zelda: Breath of The Wild, and one of them can be unlocked by collecting all 900 Korok seeds in the game. On gamer on Reddit was able to find all of them, and he revealed the weird reward you get for acquiring all 900 Korok seeds, and it's pretty shit. Literally "pretty shit". Check it out:
Called "Hetsu's Gift", the item's description says that it's "A gift of friendship given to you by Hetsu. It smells pretty bad."
This is probably the biggest joke in the game, but who knows? Maybe that golden poop has some special uses that we haven't found out yet.