The Gaki Gaki no Mi is a Paramecia Devil Fruit that grants the user three additional mouths- two on their palms and one over their heart. It grants the user the ability to consume energy and physical objects. The user becomes a Hungry Human.
The major strength of this fruit is that it allows the user to eat energy and physical objects with the mouths on their hands and chest as well as their normal mouth. To do this, the user projects an energy field out of their hands that 'sucks in' the objects and energy. Objects and energy eaten this way rejuvenate and heal the user, and can be 'vomited' up to give the consumer an advantage. Since the teeth are sharp, this also allows the user to use them effectively as weapons in battle, biting hard on exposed flesh. There is no upper limit to how much the user can eat.
The fruit's major weakness is that it effectively starves the user. The user is cursed with an unending hunger, forcing them to stay near where there is a constant source of food. The pain of starvation is described as like dying. Also, the user can only consume what he can actually get within range of his hands, chest mouth and own mouth. Other than that, it suffers from the standard Devil Fruit weaknesses.