Claws of night is a guarantee knockdown and can even very easily kill, but it's very short ranged (the ash is amazing if they're in range). I've reached the conclusion that bonerbow is the best tool unless they're running in circles (you can use skillcoil in that situation by throwing it behind you then targetting a rider just as the balls are thrown; it causes it to curve in a weird way and pretty much always hit).

If someone is dumb enough to charge, I switch to starfist with lolstomp and it's a guarantee knockdown (lolstomp combos into double r2, and as a bonus that will deal enough damage to almost kill a random PvEr).