Very strong idea, very balanced - as I have said before, the best ideas are usually the simplest. Can't get a whole lot simpler than this, and simplicity lends an elegance that often makes others go, "why didn't I think of that?"
Was it EvaRia who did the whole thing with the Shuriken? At any rate, this card is different in one important way - unlike Shuriken, the flown version does have some health, so it won't be like a Spark. Also, unlike Shuriken, it doesn't generate a new one in the hand, so you don't have a bottomless bag of flying swords.
One problem I see is that this doesn't produce any really interesting combination tactics. It's like a creature that just spends a little time in your weapon slot - could be considered a disadvantage as you need an empty weapon slot to get them through to the field. A small advantage, on the other hand, is that since it does spend time in the weapon slot, it's like a Graboid or Immortal in that creature control can be avoided if so desired.
Springboard idea to create combos - what about another card or mechanic that is fueled by the flown-weapon effect? Just like how death effects trigger stuff, flying a weapon could trigger something. In fact, this gives me a pretty neat idea for a card series I've been working on, thanks!
Definitely one of your best ideas, keep them coming. The art makes this card even cooler. You can count on my vote when it hits Crucible.
