One idea could be that Luffy somehow gains the power to slay dragons in a special arc. Maybe he encounters a dragon that is terrorizing an island and he has to use his Gum - Gum powers in a new and creative way to defeat it. For example, he could stretch his arms around the dragon's neck and then use his Haki to stun it before delivering a final blow.
In a Luffy Dragon Slayer fanfiction, Luffy could team up with other characters who also have an interest in dragon - slaying. They could form a sort of dragon - slaying crew. Luffy would bring his unique leadership and combat style, while the others could contribute their own skills like magic or special weapons. They could go on a quest to find and slay the most powerful dragon in the world, facing many challenges along the way.
Perhaps an ice dragon slayer in a post - apocalyptic world where ice dragons have become the dominant species. The slayer has to team up with other survivors and use their skills in unconventional ways to fight for survival against the dragons and other threats in the desolate landscape.
One interesting idea could be that Luffy's dragon devil fruit gives him the ability to control different types of weather related to dragons, like summoning thunderstorms or creating strong winds. Another could be that he gains the power to transform into a dragon - like form with enhanced strength and speed.
One idea could be that Dragon is on a secret mission when he accidentally crosses paths with Luffy. Luffy, being his usual curious self, wants to know more about this mysterious man who seems so powerful. Another plot could involve Dragon saving Luffy from a powerful and unexpected enemy, and in the process, they start to bond over their shared sense of justice. Maybe Luffy could also learn some new skills or gain some valuable knowledge from Dragon during their encounter.
One idea could be a crossover where Naruto meets a shadow dragon slayer from another dimension. They could team up to fight a common enemy that threatens both their worlds. Maybe a powerful dark wizard who wants to steal Naruto's chakra and the dragon slayer's magic.
In some fanfictions, Natsu might have different dragon slayer magic elements. Instead of just fire, he could have a combination of fire and lightning, which would make his attacks even more powerful and unique. Also, there could be stories where Natsu travels to different dimensions or time periods, which would introduce all kinds of new challenges and adventures for him. This could lead to him meeting alternate versions of his friends or even new characters.
Maybe Gray has to team up with a dragon in order to defeat an ancient evil that threatens to destroy the world. The dragon could have its own motives and Gray has to figure out if he can trust it.
Well, you could have an OC who is a tech - savvy dragon slayer. They create all sorts of gadgets and gizmos to help them in their dragon - slaying quests. For instance, they might have a drone that can scout out dragon lairs from a distance. Their backstory could involve a tragic event where a dragon attacked their village, and they vowed revenge. As for their appearance, they could have a cool, steampunk - like style with goggles and mechanical parts on their clothing. This would make them stand out in the RWBY universe. They could also team up with some of the main RWBY characters, teaching them about dragon - slaying techniques and learning from the Huntsmen and Huntresses about fighting Grimm.
The titanium dragon slayer could be cursed. Every time they attempt to slay a dragon, they are instead inflicted with a part of the dragon's power, slowly turning them into a half - dragon, half - slayer hybrid. This transformation makes them an outcast among their own kind and forces them to reevaluate their role in the world of dragon slaying.
One idea could be that the poison dragon slayer has to overcome a rare and powerful poison - based curse that is slowly sapping their strength. They must find a mythical antidote hidden in an ancient dragon's lair.
One idea could be that Dragon discovers Luffy's true potential during a battle against a common enemy. Maybe Dragon secretly aids Luffy without him knowing, guiding the wind or weather to give Luffy an advantage. This would add an interesting layer of mystery to their relationship within the fanfic.