The Hachi Hachi no Mi is a paramecia-type devil fruit also known as the Hive-Hive Fruit. Hachi roughly means 'Bee', but in this case is short for Hachinosu meaning 'beehive'.
This devil fruit turns the users body into a living beehive, allowing the user to conjure and control swarms of thousands of killer bees. Physical changes to the user include honeycomb shaped markings that appear on the arms, legs, and back where the bees emerge from. Like all bees they all have one sting that can be fatal if repeatably stung, which the user of this fruit is immune to. The user also has uses for the bee's honey, which can be used as sticky traps or a means for the bees to track foes.
The user has a finite amount of bees and honey which can be exhausted after an intense battle. The user must tend to the hive like any beekeeper if they are to keep the population of bees healthy. Standard devil fruit weaknesses apply.