One great 'Bruce Wayne x Reader' fanfic is 'Midnight Encounters'. It beautifully portrays the relationship between Bruce and the reader. The author does an amazing job of creating a sense of mystery and attraction. Another good one is 'City Lights and Love'. It shows how the reader gets involved in Bruce's double life. The story has great character development and keeps you hooked from start to finish.
There's also the theme of secrecy. Bruce has to keep his identity as Batman a secret, and this creates a lot of tension in the relationship. The reader may suspect something or eventually find out. A lot of fanfics play around with this idea. Also, redemption is sometimes a theme. The reader might be a character who helps Bruce find more balance in his life, between his playboy persona and his role as a vigilante.
When writing a bruce wayne x reader fanfiction, start by brainstorming the plot. You could have the reader be a new journalist in Gotham who is assigned to interview Bruce Wayne. As you write, focus on the emotions of both characters. Bruce might be guarded at first, but the reader could slowly break down his walls. Use vivid descriptions of Gotham and the Wayne Manor to set the scene. And make sure to include some sort of conflict, like a villain threatening the reader or Bruce's double life causing problems in their relationship.
One idea could be a story where Bruce Wayne discovers the reader is pregnant. He might initially be shocked but then quickly becomes protective. He starts making arrangements to keep the reader safe, like beefing up security at their home and ensuring she has the best medical care.
You can also try Tumblr. There are many fanfic writers and readers on Tumblr. Search for relevant tags such as '#Bruce Wayne x Pregnant Reader' or '#Batman Fanfiction'. Some bloggers might post links to their fanfics or even write short snippets directly on their blogs.
I really like 'A Chance Meeting' in the bruce wayne x reader fanfiction world. It starts with a chance encounter between the reader and Bruce in a crowded place. The author does an amazing job of showing how their relationship evolves from that moment. There's also 'Love in the Shadows' which shows a more mysterious side of their relationship as they navigate the secrets and dangers in Gotham.
A fanfic could explore a scenario where Harley Quinn, in her attempts to reform, crosses paths with Bruce Wayne. He initially distrusts her, but as they interact more, they start to understand each other on a deeper level. For example, Harley could be helping at a local shelter that Wayne also supports, and they gradually build a connection.
Another fanfic could be set in an alternate universe where Gotham and New York City are in some sort of alliance. Bruce Wayne and Tony Stark are forced to work together to fight a common enemy that is using both cities' resources for evil. Their different fighting styles and personalities clash at first, but over time they develop a deep respect for each other and become friends.
One aspect to consider in a Bruce Wayne x Barbara Gordon fanfic is the dynamic between their two identities. Bruce as Batman and Barbara as Batgirl/Oracle. Their relationship can be filled with tension, as they both operate in the dangerous world of Gotham's crime - fighting. They might have a mutual respect for each other's skills and a shared sense of justice. In some fanfics, their relationship could start as a professional partnership and gradually develop into something more romantic. For example, they could bond over a particularly difficult case that tests their limits and makes them realize their feelings for each other.
One common theme is the battle of ideologies. Bruce Wayne stands for a world of rules and order, while the Joker wants to disrupt it all. Another theme could be redemption, where either character might be on a path to change. Also, the theme of obsession is often present, as the Joker is obsessed with Batman and vice versa.