One great New Vegas independent Vegas fan fiction is 'The Courier's Redemption'. It follows the courier's journey after the main events of the game, exploring their moral choices further. Another is 'Vegas Under Siege' which creates a new threat to the city and shows how the characters from the game deal with it. There's also 'A New Dawn in New Vegas' that focuses on rebuilding the city in a unique way.
I'm not aware of any so - called 'famous crazy vegas sex stories' that are appropriate to share in detail. Vegas is known for its entertainment, gambling, and nightlife, but focusing on inappropriate stories isn't the best way to represent the city.
I'm not sure if there are a whole lot of these fanfictions, but you might want to check out fanfiction.net. Just search for 'Fallout New Vegas Lone Courier x RWBY' and you'll likely find some. Some might be a bit rough around the edges in terms of writing quality, but there could be some hidden gems.
A more complex plot might be that there is a dimensional rift that is causing chaos in both universes. Characters from both Fallout New Vegas and RWBY have to work together to close the rift. In the process, they learn about each other's worlds, values, and fighting styles. The contrast between the post - apocalyptic technology and magic - based abilities in RWBY could lead to some really interesting interactions and story developments.
The redemption trope can be seen too. Maybe the Courier has some past mistakes or a dark history from Fallout New Vegas, and in the RWBY world, they find a chance to redeem themselves. This can be a really deep and emotional trope, as the Courier tries to become a better person while interacting with the more idealistic characters in RWBY.
A third storyline could be them teaming up to take on a powerful raider gang that has been terrorizing the local settlements. As they plan and execute their attacks, they face challenges that test their relationship and loyalty. This could include moments of doubt and conflict that they have to overcome.
The possibilities are endless. It might be that a character has a chance meeting with a long-lost friend in Vegas, or gets caught up in a high-stakes business deal. The events in the novel could range from the exciting to the unexpected.