I'm trying to think of a good wepon for rainbow dash, the thing is that it's anthro and the wepon has to be magical to fit into the story... It's a story that's super OP so you can go nuts with the wepon powers.

A whole beltful of alchemical grenades so she can be like a mini-bomber and drop them on top of things. A little bit like the Green Goblin, I guess.

6400431
Well in the story their weapons made from the blood of ancient celestial beings so they would need to be more permanent.

6400436
Throwing daggers that would double as flechettes then might work. You can still do the whole bombing run thing by slipping in, throwing her brace of daggers, and then rinsing and repeating. If necessary, use the daggers for blitzing slice attacks too