In some fanfics, Goku and Android 18 could start as rivals but gradually develop a mutual respect and then an unexpected friendship. This could lead to them training together and learning from each other's fighting styles. For example, Goku could teach 18 some of his Saiyan techniques, and 18 could show Goku her precise and calculated combat moves.
In a 'Dbz Goku meets Bardock' fanfiction, it could start with Bardock somehow being brought back to life or time - traveling to Goku's era. They might initially have a bit of a clash because of their different upbringings. Goku was raised on Earth with love and kindness, while Bardock grew up in the harsh Saiyan society. But as they get to know each other, they find common ground. Bardock could be in awe of Goku's Super Saiyan transformations and Goku could be eager to learn about his Saiyan roots from his father. They could also form a strong bond and work together to protect the universe from new threats.
One interesting story could be about Black Goku's origin in a different universe where his transformation into an evil Saiyan had a more complex backstory involving a corrupted wish on the Dragon Balls. It might explore how his actions in that universe led to him crossing over into the main Dragon Ball Z universe.
One possible plot could be Goku and Turles forced to team up against a new, powerful enemy. Maybe a villain from another dimension that threatens both their home planets. This would force them to put aside their differences and combine their unique fighting styles.
Another place to look could be some Dragon Ball Z fan communities on social media platforms. For example, on Reddit, there are sub -reddits dedicated to Dragon Ball Z fanfiction. Members often share and recommend their favorite stories, which might include some great Goku x 18 fanfics.
Goku could develop a deeper sense of his Saiyan identity. Knowing his father, he might start to embrace more of the Saiyan warrior spirit. Bardock might change too, seeing the good in the universe through Goku's eyes.
One interesting fanfiction could be where Bulma and Goku have to team up to save the world in a unique way that wasn't shown in the original series. Maybe they have to travel to a different dimension together and face new enemies.
Well, obviously Black Goku himself is a main character. He is the center of the story in most cases as his actions drive the plot. Goku also features prominently as he is the one who has to oppose Black Goku. Vegeta is often there too, as he is another strong Saiyan and is eager to take on the threat that Black Goku poses.
Their relationship could develop through mutual respect for each other's strength. Goku, being the pure - hearted Saiyan he is, might start to see that Turles has potential for good deep down. Turles, on the other hand, could be in awe of Goku's power and gradually change his view of Goku from an enemy to a rival and perhaps even a friend.