The Dero Dero no Mi is a non-canon Paramecia-type Devil Fruit that allows the user to dissolve anything into a liquid, including themselves, by shooting beams out of their eyes. It was eaten by Artur Bacca.
The most common use of this fruit lies in the ability to shoot beams out of one's eyes to dissolve enemy weapons, as demonstrated on Law's sword. The user can also dissolve people's hearts, placing them under the user's control. The victims will die after 24 hours unless the user is knocked out beforehand.
The user is also able to access abilities similar to a Logia by dissolving themselves into liquid. No weaknesses are currently known aside from the standard Devil Fruit weaknesses.