In some fanfictions, there could be a plot twist where Draco and Harry find out that one of the Horcruxes has the power to control the minds of those who get too close to it. And Draco, being more attuned to the dark arts initially, is the first to be affected but then manages to resist it with Harry's help. This would add a lot of tension and drama to their Horcrux hunting adventure.
One interesting plot twist could be that Draco has some hidden knowledge about the Horcruxes from his family's dark secrets. Maybe his mother had unknowingly passed on some crucial information to him that helps Harry and him in a very unexpected way during the hunt.
One interesting plot twist could be that the last Horcrux is not an object but a person no one suspected. For example, it could be a seemingly innocent bystander who has been under Voldemort's control all along without anyone realizing.
Harry is brave and impulsive. His eagerness to destroy the Horcruxes quickly drives the story forward. Draco, on the other hand, is more cautious and calculating. He might slow down Harry at times, but also ensures they don't rush into dangerous situations blindly.
Well, in some fanfictions, a plot twist might be that Draco and Harry are forced to marry by a magical contract that was hidden for ages. And as they try to break it, they actually fall in love. Or perhaps a twist where Draco is actually a spy for the good side all along and their marriage is part of a grand plan to expose the remaining Death Eaters. There could also be a twist where Harry loses his memory and Draco has to make him fall in love with him all over again while dealing with the wizarding world's reaction to their union.
One possible plot twist could be that Draco has a hidden agenda all along. Maybe he's actually trying to protect a particular Horcrux for his own reasons. Another could be that he discovers a new Horcrux that no one else knew about, throwing the whole hunt into chaos.
In some of these fanfictions, a great plot twist is that Draco, being a Muggleborn, is actually a long - lost heir to a powerful Muggle - related magical artifact or prophecy. This throws the whole wizarding world into chaos as different factions try to either use him or protect him. Also, there could be a plot twist where Draco uses his knowledge of the Muggle world to outwit dark wizards. Since he has a connection to the Muggle world that most pure - bloods don't, he can come up with strategies that are completely unexpected, like using Muggle technology in a magical way to defeat his enemies.
In some fanfictions, a great plot twist is when Draco is on the verge of making a really bad decision, like joining the Death Eaters completely. But then he discovers his true relation to Severus. This changes his perspective as he realizes Severus has been secretly protecting him all along. It makes him question his loyalty to the Dark side. Also, there could be a plot twist where Severus has to choose between his loyalty to Dumbledore and protecting his son Draco, which creates a lot of internal conflict for him.
One interesting Harry and Hermione Horcrux fanfiction could be 'The Horcrux Hunt'. In this fic, Harry and Hermione embark on a dangerous journey to find and destroy all the Horcruxes together. Their friendship deepens as they face numerous challenges along the way.
In some of these fanfictions, a great plot twist is when Hermione gets cursed and Draco has to find a way to break it. During this process, they learn more about each other's true selves. Also, it could be that Draco is under the influence of a dark spell that makes him act against Hermione, but she believes in the good in him and tries to break the spell, which deepens their bond in a very unexpected way.
One interesting plot twist could be that when they go back in time, they find out that their families were actually friends in the past. This completely changes their perception of each other. Another could be that they accidentally change a major event in the past, which has unforeseen consequences for the present wizarding world. For example, they might prevent a certain spell from being created, which then alters the balance of power between different wizarding factions.
In some fanfictions, when Harry absorbs the Horcrux, it could lead to a moral dilemma within him. He has to struggle with the dark influence of the Horcrux while still trying to be the good wizard he is. This internal conflict can make for a really engaging story, with Harry constantly fighting his inner demons and trying to separate his own identity from that of Voldemort's.