The Ougon Ougon no Mi (ougon being the Japanese name for gold) is a Logia Devil Fruit that allows the user to turn into and control gold.
The fruit resembles a large, green plum, with swirls on it.
The main strength of the fruit is that one can control anything with even the faintest hint of gold in it, even gold dust. Also, this essentially makes the user a walking piggy-bank, as they can create gold from their body at will, without anyone being able to call it fake.
The weakness of the fruit lies in the weakness of the material itself; any weapon and armor made from gold isn't too sturdy, and is easily breakable when faced against stronger materials.