About Pika Pika no Mi
The Pika Pika no Mi is a Logia-type Devil Fruit that allows the user to create, control, and transform into light at will, turning the user into a Light Human (光人間, Hikari Ningen?, Crunchyroll: "Light-Man"). It enables the user to move at the speed of light and transport themself by means of reflection. It was eaten by Borsalino, also known as Admiral Kizaru.
Like with all other users of Logia Devil Fruits, the user of this fruit is able to control, create, and transform into an element. In this case, Borsalino is able to control, create, and transform into the element of light. As such, the user is able to utilize light-based attacks, including shooting laser beams from their hands, fingers, feet, or even eyes (which are capable of causing massive explosions), summoning light flashes to blind opponents, and undergoing partial transformations into light itself that enable physical attacks that connect at light-speed, which can cause devastating damage.
The user, like any Logia, is able to transform into light to let incoming attacks pass right through them. The user is also able to travel at the speed of light, form hard light constructs, create or split into shining particles for locomotion, regeneration or even multiplication, and reflect themself between surfaces to any desired location. The user is able to transform and move at such speed that their movements are not even detectable, with Borsalino acquiring food for Luffy so fast nobody present even noticed, made all the more impressive that individuals with powerful Haki were present.