Monster Chopper

Monster Chopper is a form Tony Tony Chopper takes when he has eaten 3 Rumble Balls within 6 hours.

It seems that the consumption of three Rumble Balls in under six hours created a new Point in which he is standing similar to Heavy Point, but possesses an oddly misshapen head and antlers, as well as an incredible (likely more than twenty feet, or about the size of an office building) increase in height and strength. Chopper's fur is also lengthened in this form. Chopper also loses all consciousness and goes completely berserk in this form. Also, this form appears to be a combination of all Chopper's points, not including Brain Point and Arm Point (Heavy Point stance, Walk Point speed, Horn Point horns, Jump Point legs, and Guard Point hair). Doctor Kureha told him after he had used it for the first time, that he had leveled an entire village on Drum Island while in this form. Kureha also commented on this form being that of a true monster; a danger to friend, foe, and even Chopper himself. According to Zoro's observation, this transformation appears to be lethal to Chopper, as the amount of energy needed to maintain the form is too much for his body to handle. The only known way to end this form is by placing Chopper into the sea; this is perhaps how Chopper's Monster Point was stopped during the first time he used it, as his aftermath is similar, with him unable to move.

Davy Back Filler Plothole
Although Chopper shouldn't eat three Rumble Balls within 6 hours, in the filler part of the Davy Back Fight he took two right after another in the "Hit and Deadball" game. Thus this is one of the major plotholes Toei created. However because this was done before Oda got to that part in the manga, they had no way of knowing.