The Golden Flower is a collectible item in Momodora I.
The item itself has no gameplay effect, its just for collecting purposes.
It can be found shortly after obtaining the ESP Gun. One room after you obtained the gun, drop down on the lower floor. Instead of going to the left to progress the game, go right into a pair of rooms that look like they contain golden leafs. The Golden Flower can be found in the second room on a pedestal.
It is a useful for farming munnies, since it doubles the amount that gets dropped by enemies. Belltower Garden, the area it can be bought in, is also very nice for farming munnies.
This item is rather nice with a Star Magnet, since it will drag all money dropped towards you, automatically collecting it.
The Golden Flower, however, becomes drastically less powerful in New Game+, since money shouldn't be that much of an issue at that point anymore.