Circle of Friendship

So you're in a show which is near the idealistic end of the Sliding Scale of Idealism Versus Cynicism, and the Big Bad (often powered by hate or another negative emotion) is way too powerful for you to beat: He shrugs off all your Applied Phlebotinum like it's nothing, he laughs while ignoring your ultimate attacks, and he is about to destroy your whole squad just by sneezing at them.

It's time to form... the circle of friendship!

All the heroes get into a circle (or a love heart shape if the writers don't mind being really cheesy) and generally start to sing and wave their arms around. The Big Bad may laugh at the circle, but it's generally the last mistake he makes...

A beam of pure friendship/love will fire at the Big Bad, often instantly killing him. No matter how strong the Big Bad is, if it hits him, he'll instantly either be reduced to a corpse or magically turn good. Nothing can resist it. It is the ultimate incarnation of The Power of Friendship and the Combined Energy Attack.

Of course, there's no guarantee that this will work on the next villain...

Compare Care Bear Stare.

Examples of Circle of Friendship include:

Yu-Gi-Oh!: It was the Shorttank's invention.
- Even better in the Abridged Series. "Tea... is that permanent marker?"
Sailor Moon: The Sailor Planet Attack!
The Care Bears were fond of this move.
The end of Pedro's story in Excel Saga parodies this (specifically the Sailor Moon take on it, with a fair doze of Dragon Ball thrown in; "Na-be-ha-me-ha!"); to add to the fun, everyone on his side has afros.
Osu! Tatakae! Ouendan, its sequel Moero! Nekketsu Rhythm Damashii: Osu! Tatakae! Ouendan 2 and their associated game Elite Beat Agents all end with the inhabitants of Earth singing and dancing together to fire a giant hadoken of love and music at whatever was going to destroy the world today, be it a giant meteor, the mothership of an army of music-hating aliens, or the dying sun.
Digimon Adventure 02 used one of these, as did 01.
Played distressingly straight at the end of the Japanese-only Transformers series: Headmasters. Bonus points for the members of the literal circle being giant robots. Double bonus points for it being the idea of the Token Human. Triple bonus points and a 1-up for him being given the idea by the angsty loner.
Literary example: In Stephen King's IT, the main characters do this to help a hospitalized main character take on a Brainwashed and Crazy nurse.
In the final battle of EarthBound, your attacks are mostly ineffective against the Big Bad, and so the only way to beat him is to use Paula's "Pray" command, which will start a special Cutscene-like event during the battle and all of the people that the characters met during their travels, including the player him/herself, pray for the destruction of Giygas. After this command is used a few times, the player will deal hundreds of thousands of damage to Giygas, defeating him.
Played with in the Youtube video College Saga, where the group has to face a tree, and decide to sing a song when unable to damage it by normal means. Upon singing a song that has nothing to do with the "game", the tree is instantly destroyed.
A running theme in Princess Gwenevere and the Jewel Riders.
It lacks the visible magical beam, but in the first of Tamora Pierce's Circle of Magic books, the protagonists are trapped in a cave during an earthquake, and using a circle of woven thread Sandry had on her from the beginning, they infuse it with their magics and by shared power cause the cave to not crush them and the thread gives off light so they can see (Sandry is afraid of the dark). This thread goes on to have more significance later.
The SD Gundam Force members Captain, Zero and Bakunetsumaru had something like this. It became a Crowning Moment of Awesome during the final episodes.
In My Little Pony Friendship Is Magic, the mane six defeat Nightmare Moon in this exact way, though it takes the Elements of Harmony to actually create the "friendship beam." They do roughly the same thing to Discord at the end of part 2 of "The Return of Harmony".
- In the "Hearth's Warming Eve" episode, it's revealed that the founders of Equestria also used this, by accident, to destroy the Windigos, a group of spirits who feed off of The Power of Hate who were attempting to freeze the world. Instead of the rainbow from before, it forms a flaming heart that incinerates the Windigos. It would appear that weaponized friendship is pretty much the method of choice in Equestria for dealing with Eldritch Abominations.