Well, 'The Unlikely Friendship of Danny and Dash' is worth checking out. It starts with a small incident in school that makes Dash re - evaluate his view of Danny. As the story progresses, they form an unlikely friendship that is both heartwarming and full of humor. The author does a great job of exploring their characters and how they change in relation to each other.
One popular Danny x Dash fanfiction is 'Unexpected Bonds'. It delves into how Danny and Dash, who seem like polar opposites at first, start to understand and care for each other in a really interesting way. Their relationship develops gradually, with Danny's ghost - fighting side and Dash's jock persona creating some really engaging interactions.
There's also 'Danny and Dash: A New Alliance'. In this fanfiction, a common enemy forces Danny and Dash to team up. The story is great because it shows their growth as they learn to rely on each other's strengths. Dash discovers that Danny is not as weak as he thought, and Danny sees that Dash has a more complex personality than just being a bully.