A ninjutsu with pre-eminent destructive power, caused by wildly spinning chakra inside one's palm and compressing it to a high density — the Rasengan. Using the same essentials, but also rapidly increasing the amount of chakra used, results in the Big Ball Rasengan. It was created by Naruto Uzumaki during his training with Jiraiya. At first, Naruto needed a shadow clone to form the Big Ball Rasengan and help him wield it. But as he got more skilled with it, Naruto can now wield the attack with one hand, but still needs a shadow clone to help him create it. Compressed to an even higher density than before, the chakra is released all at once as soon as the technique hits the target, releasing an extraordinary destructive power. Proportional to this power, the amount of chakra it consumes is also extraordinary. With him possessing the Nine-Tails' chakra, it could be said that this technique is for no-one but Naruto.
Like the Rasengan, this technique does not require hand seals, but it does take some more time to create. When used on "Itachi", it was powerful enough to leave a fairly vast mark onto the ground sending his target way back and taking out some tree's.
The anime shows how Naruto created this technique. Naruto, while training to break out of genjutsu, accidentally released his chakra and created a huge Rasengan. It was bigger than an average Big Ball Rasengan but smaller than the Sage Art: Big Ball Rasengan.
Minato Namikaze's normal Rasengan is roughly the size of the Big Ball Rasengan.
When Konohamaru used this technique in the OVA, he was able to use it with one hand.