In Manchester Lost, this ends up having an interesting twist. Crowley has a shoulder angel and demon represented as Inner Aziraphale and Inner Hastur. Aziraphale has an Inner Crowley and Inner Raphael. Both sets are hilarious.
In Kyon: Big Damn Hero, Achakura and Kuyou transform into these tempoarily, but neither of them quite get Black and White Morality.
Calvin and Susie have an argument in In Love and War. In responce, Spacemann Spiff and the Dictator-for-Life appear. Shortly afterwords, a Hobbes and pirate Hobbes appear as well. As it turns out, the entire shoulder angel secquence was All Just a Dream.
During the Hot Springs Episode of Tengen Toppa Gurren Solvernia, they try to talk to Kamina. The Bad Angel argues that Kamina should see the girls' side, but the Good Angel tells him to not do it, because Nia is among. Then the Bad Angel reminds that Nia shouldn't be there anymore, and thus the Good Angel tells Kamina to continue with his plan.
Played in a literal sense in Ah! Archfall!, in that Jago actually has an angel AND a devil.
In a Ranma 1/2 doujinshi (Mantou 12) Ranma's good rightious side is represented by Amelia Wil Tesla Seyruun, while his bad lustful side is represented by Lina Inverse
On chapter 3 of "Days of Futures Past What Does That Mean It Kinda Sounds Sexy" a Naruto Young Justice crossover Naruto gets excited that two of his shadow clones argue on ether doing the right thing or turning his back on the young heroes. He demands that both shadow clones transform in order to make their points first transforming into Naruko in a sexy devil costume and a white robe wearing harp player but choices to flow the good clone due to the fact the bad one snapped at him for being indecisive.
MLP Next Generation: Love Conquers All! Avarice Takes It All! has a variation: While Nidra doesn't immediately don the Orange ring that chooses her as a host, mere exposure to its Light of Avarice awakens all her darkest and most selfish impulses, which constantly battle her conscience in the form of internal dialogue.
In A.A. Pessimal's Discworld fic Hear Them Chatter On the Tide, red-haired Assassin Johanna Smith-Rhodes is caught, at a fraught time, between the Two-to-the-Power-Three Virtues and the Four-Squared-Divided-by-Two Vices. She has the Vice Anger on her right and the Virtue Fortitude on her left, both claiming her as an earthly avatar, one suggesting she go postal and use unfettered agression, the other counselling that her anger be productively channeled to bring about bloodless change. Johanna acknowledges that both have a point. Then forces the opposed qualities to clasp hands. Anger and Restraint both scream with agony as their energies cancel each other out, leavimg only an Assassin who has just won the Teatime Prize (for most inventive inhumation of a supernatural entity).
"People created you." she said. "Therefore both of you are part of me. I accept you both. But I remain human end free to choose!"