Moonflair Spellblade
So close to a decent item. But never currently viable to do always a stronger item. Give it a small-on-hit effect (adjust cost) and it would probably see play.
I'm thinking: Unique Passive: Basic Attacks on champions steal 10 move speed, stacks up to 5 times. or something like that. It could be a viable item on Diana, Oriana, Fizz, Ekko, Aurelion or other AP close range fighters. It would also be nice to see more item diversity for these champs. They all build nearly the same thing every time.