Another plot development could be that the hand cannon was created by a group of rebel wizards in the past who were against the established magical order. Harry using it could make him a target of those who still uphold the old ways. This would put him in a difficult position as he tries to use this new tool for good while facing opposition from within the wizarding community.
Maybe it was given to him by a mysterious stranger. This stranger could be someone who has been observing Harry from afar and believes that he is the only one who can handle the power of the hand cannon. The stranger appears out of nowhere, hands it to Harry, and then disappears again without a trace.
Maybe Harry starts using lethal force against Death Eaters. This could lead to a more vengeful and darker path for him. His friends might be divided in their support for him.
One popular 'Harry Potter uses sleight of hand' fanfiction might involve him using sleight of hand to perform magic tricks in a Muggle - style way during a Hogwarts event. It could add a unique and fun twist to the magical world we know.
One interesting plot could be Harry struggling to fit in with the Slytherin ideals at first. He might be constantly at odds with some of the more traditional Slytherin values like pure - blood supremacy. But then he could gradually change the house from within, making his Slytherin peers see that not all Gryffindor traits are bad and vice versa.
In some of these fanfictions, Harry might gain god - like powers and use them to reshape the wizarding world. For example, he could end all forms of dark magic at once. Maybe he uses his newfound divinity to bring back lost loved ones, like his parents, in a way that doesn't disrupt the natural order too much.
In some of these fanfictions, Harry might start exploring the dark art of necromancy secretly. He could be driven by a desire to bring back his lost loved ones, like his parents. This often leads to him having to hide his newfound interest from his friends at Hogwarts, creating a lot of internal conflict as he struggles between what he knows is right and his longing for his family.
One interesting plot development can be that Harry levels up his Occlumency skills to an extraordinary level. This would mean he can not only block Voldemort from invading his mind but also be able to read the minds of others to some extent. This would give him a huge advantage in battles and in uncovering mysteries. For instance, he could use this skill to figure out the true intentions of some of the more ambiguous characters in the wizarding world, like Snape. And it would completely change the dynamics of his relationship with other characters, as they would be more cautious around him knowing he can peek into their thoughts.
In some fanfictions, Harry inheriting a fortune could lead to him having more political power in the wizarding world. He could use this to change laws that are unfair to certain magical creatures or groups. For example, he might fight for the rights of house - elves. He could also use his money to fund research on dark magic prevention, making the wizarding world a safer place.
One interesting plot development could be the exploration of Harry's relationship with Sirius Black outside of prison. Maybe they go on adventures together, hunting down remaining Death Eaters. Another could be Harry's improved skills in Defense Against the Dark Arts, as he now has Sirius as a more regular mentor. And perhaps there are new magical creatures introduced that Harry and his friends encounter during their post - Azkaban adventures.
Another possible plot development is that the snake is actually a transformed wizard or witch under a curse. Harry, during the encounter, discovers this and tries to find a way to break the curse. This could involve a long and difficult journey, seeking rare magical ingredients and spells, and facing many challenges along the way. It could also bring up some moral dilemmas for Harry, like whether to trust the snake - who was once a human - completely or not.