((I can easily see this one not being accepted, but it should be balanced.))
Name: Saisei Saisei no Mi (Regeneration Fruit)
Capabilities: This devil's fruit has a singular, passive ability attached to it. Initially, it can seem like the best thing in the world. The power granted by this fruit is that of instantaneous regeneration of any cell structure. This process is rapid enough that the user can not even be decapitated if it were tried. (Of course, if the blade is wider than their neck, it works. Guillotine anyone?) However great this may sound, there are a number of negative effects the user takes on because of this ability. First and foremost, the user still experiences pain. Although it disperses quickly, it can be a distraction against them. Secondly, the ability does nothing to lessen the force of attacks. If a user of this fruit is hit hard enough to be knocked out or sent flying, you can expect that to happen. Out in the open ocean, this is somewhat of a problem for a devil's fruit user. As the third point, the rapid healing will remove bullets and shrapnel from the body, but not the same for infectious diseases. Since the wound has no time to bleed or even have disinfectant applied, the chance of any such disease in a user of this fruit is significantly increased. It is advised that they have constant access to antibiotics. Finally, the greatest negative effect of this fruit is that of halted muscle growth. Generally, a person becomes stronger by first weakening and or slightly tearing their muscles through physical exertion. Since a user of this fruit will have his or her muscles healed before they can be significantly weakened or torn, they can not gain any strength. It would be rather problematic for someone if they were to have eaten this fruit as a child considering this fact. They will not however, become weaker overall. They will still suffer fatigue from a battle however.
Type: Paramecia