Parent and Child Rasengan

The Parent and Child Rasengan is cooperation ninjutsu whereby two shinobi, most often a user and their child as the namesake suggests, combine their Rasengan into a massive sphere, which is then thrust into their target.

Naruto and Minato's Version
Naruto and Minato, in their Tailed Beast Modes and with Naruto in Sage Mode as well, collaboratively create a Rasengan of their chakra avatars' size, then slam it into the target. This attack was strong enough to push back Obito Uchiha as the Ten-Tails' jinchūriki.

Naruto and Boruto's Version
Boruto starts off by generating a tiny Rasengan. Clasping Boruto's hand, Naruto then adds his own chakra to the Rasengan, forming a gargantuan sphere which dwarfs both in size. Boruto used this technique to kill Momoshiki Ōtsutsuki, himself deemed a threat greater than Kaguya Ōtsutsuki by Sasuke Uchiha.

Trivia

 * Though clearly not being a normal Rasengan, it was simply called Rasengan in the manga.