Theoretical Item Builds
The Good, the Bad and the Awesome
If any marskman can just stand still and still poke the hell of Gwenaël, Caitlyn's the name. The laning phase will be painful since she all of her abilities will outshine Gwenaël's and only by late game he might rise to the challenge... that's if Caitlyn doesn't close the game earlier.
While Nocturne's Paranoia's global DARKNESSSS! does nothing against Gwenaël, he's one of the few junglers that can pull a gank against the marksman without being detected by the sound mechanic and Gwenaël is easy prey to the assassin due to utter lack of mobility.
If you're laning against a Lux support, pray to all gods imaginable that your support isn't sleeping on the job and makes sure you know where she is at all times, because she can melt you in a swift combo without moving a single step and while being outside of your grasp.
On the spectrum of laning, Vayne lies in the opposite side of Caitlyn, since Gwenaël can abuse her poor laning phase by constantly harassing her with either Smite the Wicked or Deliverance being used safely even if she's behind her minion wave. If Vayne gets cheeky and uses Final Hour, Gwenaël just laughs due to him ignoring stealth and makes her flee with an inescapable Kyrie Eleison.
Speaking of ignoring stealth, Evelynn can't even gank properly Gwenaël since she's too reliant on not being detected and he'll probably hear her the moment she steps on the river. And, unlike the likes of Shaco or Rengar, she doesn't have any good tools to close the gap before Gwenaël reacts.
Although Sona's musical theme doesn't interfere much with the sound mechanic, she's a sitting duck for Gwenaël: she has to move to even poke properly, her heals aren't enough to mend the incoming harassment and her lack of mobility can lend her cursing at the Altars of Ascension. Furthermore, the tiniest of mistakes on casting Crescendo will kill her since a cast of Kyrie Eleison at such a close quarter will make her melt under the arrows.
Gwenaël loves early game junglers that can secure him a smooth transition to the late game, but he loves even more junglers that know how to make a lot of sound when ganking, and Lee Sin excels at both fronts. Not only that, a well-placed Altar of Ascension will make the blind monk even more of a mobile threat with tons of damage.
Janna is everything Gwenaël could ask for: peels for days that not only complement his harassing behaviors, but are perfect to proc the sound mechanic; powerful disengage to compensate for his lack of mobility; finally, she has a shield that increases his AD and can stack with his Altar of Ascension. She even has a nice heal!