Sorry if this is a repost but i haven't been here long and haven't seen it.
Of course you must have a shaman to do this trick and you must also have at least two ranks of windfury.
1. Cast a lower rank windfury on your weapon(s).
-You may have to cancel your weapon buffs already on your weapons to do this.
2. Open a trade window with whoever you desire to recieve windfury.
3. Have them place their weapon in the Will Not Be Traded window.
4. Click on a higher rank of windfury (or simply a different one than what is casted on your weapon).
5. When you click on windfury it will give you a little hand to cast the spell instead of auto casting onto your weapon.
6. Click on their weapon in the trade window and complete the trade.
- It will not say their weapon has windfury when you mouseover it but they should have recieved the buff.
I tested this a couple days ago on 2.3 so it SHOULD still be working, I don't play the on the shaman much, and of course, this is Emu only.
Also I noticed while I was doing this that sometimes when i would relog the buff would refresh itself. Not sure why it would, and then wouldn't other times. It is at least 30 minutes of fun though.