Tsuna's Limit Break:

Master Die: Tsuna was an early experiment that would later be perfected with Vincent. The energy of the experiment was still in its infancy and was difficult to control without Tsuna losing his mind. As such, the scientists devised a way to contain the energy and release it only a little. They joke at the chance of Tsuna being chosen for the experiment and used a die to contain his transformation. The die contains different monster energy and DNA and the number decides how far the transformation goes. Before Tsuna was put to sleep, the test subject rolled a 6 and went berserk. They were forced to put Tsuna to sleep for that very reason and since the die was linked to Tsuna's soul it also reset to its basic form, a Nibel Fang. The die has the ability to bring back the lost energies as well as gain new one from enemies Tsuna fights.

1: A single arm.
2: Both arms. 
3. Both arms and a leg.
4: Both arms and legs.
5. Both army, legs, and the torse.
6: Entire body.
Note: 6 is extremely dangerous, but also powerful. When rolling the die, Tsuna chooses which energies to use, but if its the highest level he has, Tsuna loses himself to the monster. He is forced to attack as the monster does and his target is random, including allies. Also, if Tsuna is attacked he will counter attack the following post out of instinct. If he uses a lesser level, his target is still random, but he has an idea of who's an ally and who's an enemy. If the monster has multiple attacks that is also random. I'd like to to last a few rounds, but when its over Tsuna can't react at all due to the shock of regaining his sense of self, no matter the level he chooses.