One great Percy Jackson Avengers fanfic is 'The Demigod and the Superheroes'. It has an exciting plot where Percy teams up with the Avengers to fight a common enemy that threatens both the mortal world and the world of the gods. The character interactions are really well - written, like when Percy shows the Avengers his water - manipulation powers and they are all in awe.
Another interesting one is 'Avengers Meet Camp Half - Blood'. Here, the Avengers end up at Camp Half - Blood. They learn about the demigod world and Percy has to play the role of a guide. The story is full of humorous moments, like when Tony Stark tries to build some high - tech gadgets for the demigods but they end up backfiring in a comical way.