If You Won't, I Will

The Chosen One is confronted with his ultimate destiny. The prophecy is about to be fulfilled.

But the Chosen One doesn't want to. Maybe he's refusing the call. Or maybe he's just sulking. Maybe he's too busy wallowing in his own Wangst. But for whatever reason, the Chosen One doesn't want to do the job that only he can do.

So his friend goes out to do it instead, saying, "If you won't, I will." This is usually an ultimatum, because everyone knows that the friend can't do it, that only the Chosen One can do it.

This leads to either the hero stopping his friend before he goes to get himself killed, or the hero lets the friend go and gets himself killed. The latter usually triggers a Roaring Rampage of Revenge that fulfills the Chosen One's ultimate destiny.

The destiny part isn't really important. It could simply be that the friend is incompetent and the hero knows that he'll get himself killed/captured. And the friend probably knows this as well, so he uses it to spur the hero to action.

Anime and Manga

 * One of the times Shinji considers quitting in Neon Genesis Evangelion, Rei comments that if he does, she'll take over his duties.
 * In the first episode, Gendou threatens to send the grievously injured Rei to pilot in Shinji's place, effectively blackmailing Shinji into being a pilot to begin with.
 * An inversion of this occurs in the 13th Dragonball Z movie where Goku ponders to himself, "If I don't, who will?!"
 * In Ginga Densetsu Weed, after finally defeating Hougen, Weed was given the chance to kill the evil Great Dane. But when Weed refuses, Gin goes forward and goes to kill Hougen, saying he will have to kill him if his son doesn't. Three guesses what happens next.
 * This is also used by Weed when GB backs out from saving Sasuke from a massive guard dog.
 * Yahiko shouts something vaguely along these lines when finally giving up on Kenshin during his Heroic BSOD in the Jinchuu arc, and a bit later winds up in a one-on-one fight with the guy who has a cannon for an arm. It's not a Curb Stomp Battle, incredibly, but Yahiko is clearly going to die. Tsubame makes her way into the Ultra-Slum of Doom to tell Kenshin about how hard Yahiko is trying and how much he needs Kenshin now, and that's what finally brings him back.

Literature

 * In Robert A. Heinlein's The Puppet Masters, the hero Sam is asked to allow one of the title monsters to take control of him as an experiment. He refuses, and discovers that his girlfriend Mary has volunteered to do it and will be going in his place. He reverses himself and agrees to take part.
 * In Harry Potter and the Half-Blood Prince, Snape.

Live-Action TV

 * In Heroes, Hiro panics at having not killed Sylar, so Ando sets out to kill Sylar instead. Sylar kicks Ando's powerless ass with ease and nearly decapitates him before Hiro shows up. This actually happens quite a lot with Hiro and Ando. Hiro gets all whiny, then Ando sets out to do it, the two get seperated and mad at each other. Then Hiro comes to his senses and saves Ando just before he gets himself killed. Then they're all happy, at least, until it happens again...
 * In Buffy the Vampire Slayer, Giles does this sort of thing a few times for Buffy, but fulfils the trope most clearly in the season one finale. Buffy, hearing that she is prophesied to confront the Master and die, quits in horror. Giles decides to go after the Master himself in an attempt to save her, but a newly-resigned Buffy knocks him out and heads off, planning to at least take the Master down with her.
 * In Power Rangers Jungle Fury, after Lily gets a sudden personality change, she becomes a complete jerk, wasting time in the pizzeria they work in. Fellow worker Fran, who at this point figured out their secret, calls her down on this behavior. And when Lily refuses to budge, Fran takes Lily's morpher, saying this trope. A Cat Fight ensues.

Mythology

 * Related to Achilles in His Tent, as noted above, and in fact the Iliad is a perfect example of this trope: Achilles' friend Patroclus goes into battle in his stead, and gets himself killed. His death spurs Achilles to rejoin the fight.

Western Animation

 * The Fairly Oddparents: the Crimson Chin sulks, so his sidekick, Cleft, tries to do the work for him. But after Cleft gets in trouble, the Crimson Chin wakes out of his Wangst to save him.
 * In Up, Russell does this to try and get Kevin back when Carl went into his Heroic BSOD.