As a result, it's become a Stock Phrase for describing any conflict between particularly strong or particularly stubborn individuals.
In the hands of a single warrior, that warrior would be unstoppable. The Master then clasps their hands together, declaring the two together to be "the warrior.". Referenced in the anime of Trigun by Hoppared the Gauntlet, who declares himself as an invincible shield and Vash's guns as an unstoppable spear.
In Pokémon, Rampardos is described as the unstoppable force/spear that can break any shield and Bastiodon is described as the immovable object/shield that can't be broken. They battle. So you might be wondering what happens when Roark's Rampardos battles his father Byron's Bastiodon.
In Naruto, the legendary Third Raikage possesses an impregnable defense and indefensible offense through using his lightning chakra cloak . The only way he could be wounded was to turn his attacks on himself . According to Go Nagai, Shin Getter Robo is the unstoppable force while Mazinkaiser is the immovable object.
Raiden wins due to his sword's properties being able to compromise Wolverine's skeletal structure. The Hulk vs. Doomsday episode is described as an unstoppable force facing an immovable object, respectively. And in this case, the immovable object Doomsday won.
In Blink, the Kyuubi tries to destroy the Shinigami's seal and learns what happens when an unstoppable force (himself) meets an immovable object (the seal): time stops until he stops trying. Because Naruto's immune to it , he gains the moniker of "Blink" because if you close your eyes, even to blink, when facing him they'll never open again.
Invoked directly in the second Superman / Spider-Man crossover, when Superman calmed down The Hulk by planting himself to the ground and let the Hulk hit him, thinking that when he decided to become the Immovable Object, no Unstoppable Force could move him.