In chapter two, the Ember Trial becomes this with a good enough diplomacy skill. With nothing but some quick thinking and a silver tongue, you utterly demolish Torio's accusations bit by bit, point out every single hole and flaw in her plot, and effectively humiliate her in front of the entire courtroom. And when Torio pulls out her trumpcard, the Sole Survivor of the Ember massacre's testimony, you and Shandra manage to convince the witness that she may have been tricked, rendering her testimony (which Torio's arguements hinge on) moot. And it doesn't stop there. After you're done humiliating Torio in verbal warfare, you and Sand proceed to call your own witnesses, the various people you've helped up to this point, further discrediting the prosecution. Yes, Torio manages to retaliate by forcing a trial by combat, but its clear that she's been utterly trounced. And the kicker? After all is said and done, you actually get a background feat that details how your performance was so incredible, it has instantly become the stuff of legends in the legal community, and your words will be regarded as an inspiration for legal officers for centuries to come.
With a high enough perform stat you can do all of the above in song.
Related to the above: During your preparations for the trial by combat, Khelgar will burst into the room and insist he fight in your stead. When asked why, he goes on an epic rant about how Torio's actions made the trial a sham, that the coming duel was ultimately pointless and unfair since you had already fairly proven your innocence, and how Luskan's actions have made a mockery of justice. It really shows how far he's come from the arrogant Blood Knight he began as.
And in doing so he unwittingly fulfills one of the requirements to become a Monk: gaining a true understanding of Justice.
Late gate fights, typically in the third act, are something special especially when you know it's a climatic battle and you can cut loose and use everything. The three-way fight between your party, a huge dragon and a encampment of giants is pretty good, and so is the last battle where every possibly party member joins in to kick the King of Shadow's butt.
Neeshka gets one: If you have high enough influence with her, she defies a Geas to stay on your side, defying Black Garius and basically staring death in the face for you, all because you were nice to her.
It's possible to make Ammon Jerro feel remorse for killing Shandra. At first it seems that he's irredeemable, invoking I Did What I Had to Do. However you point out that his self-righteousness means that he'll often act with incomplete information, just like he did with Shandra. This causes a Heroic B.S.O.D., and after a moment of silence, he admits that you're right.
In the final battle, Black Garius gives him the chance to join him in service to the King of Shadows, even offering to bring back Shandra so they can bond as family. Jerro utterly shuts him down.
Ammon Jerro: You could promise all that and more, Garius. But for all your empty promises, I have seen the one I follow accomplish so much more. And Garius, for mentioningShandra to me, I shall enjoy watching you die.
Mask of the Betrayer
Learning the "Heal Allies" power by healing the Woodman. It sounds simple on paper, but in practice, it means that you, a normal mortal in Faerun, manage to take a curse created by a god that can do nothing other than devour spirits, and force this mindless thing to defy it's own nature. In the words of the Woodman, you teach it to obey you.
The meeting with Myrkul. You meet a dead god and walks on his corpse. And after speaking to him and learning that the soul-eater curse, and therefore you, who sustains his very existence, can devour his soul. That's right, you can eat the soul of a dead god using a curse that he created to prolong his life.