Duskblade of Draktharr and Kha'Zix
Since this item was announced, I was waiting for the opportunity to test it on my favorite AD assassin, Kha'Zix.
This week, I finally had the opportunity, and I must say: This item is fantastic for Kha'Zix. It increases his burst by a lot and somewhat mitigates his reliance on isolation. Remember the times where Kha's Q used to do damage based on the enemy's missing health? Now you can have the same feeling as before with this item.
I don't know why people said that this item would be weak on Kha'Zix. As long as you are not behind, it is actually a fantastic item to buy. Also, contrary to what many people say, you need to auto-attack as Kha'Zix; he isn't completely non reliant on auto-attacks. He needs to auto to apply his passive, which also allows him to apply Thunderlord's Decree because the auto counts as 2 procs for Thunderlords - both the auto-attack itself and the passive; so, with just one Q and one auto, Kha can apply Thunderlords. Combine that with Duskblade, and you can murder any champion that is isolated and is not a full tank (though even full tanks must be wary of trying to duel Kha).
I think that the only reason why Kha'Zix is still considered weak - his winrate actually decreased after Duskblade was added to the game - is because other assassins, namely Zed and Talon, have stronger kits and take better advantage of Duskblade than Kha'Zix currently. In other words, while Kha'Zix was buffed, other assassins were buffed too, and Kha'Zix remains outclassed by them.