Rasengan is ball of chakra created in the palm of the user which rotates at high speed. This Justu was created by Minato Namikaze by observing a Tailed Beast Ball. The Rasengan is said to be the highest form of shape transformation.
Throughout the series, there are 7 different Rasengan Users, which are listed below.
7. Konohamaru Sarutobi
Naruto taught Konohamaru how to use the Rasengan. Although, he did take some time to learn this Justu, Konohamaru was also able to add his Wind Release to this techniques. At first, he also used this technique via a Shadow Clone, but later, he was able to do it Single-Handedly. Konohamaru is also capable of using Fire, Wind and Yang Release.
6. Kakashi Hatake
Minato Namikaze taught Kakashi how to use the Rasengan. He originally intended to add his Lightning Nature to this Jutsu and create Lightning Release: Rasengan. But, after adding the nature manipulation to it, he ended up creating the Chidori instead. Nevertheless, Kakashi is able to use the Rasengan, though he prefers his own original Raikiri.