This... uhh ...happened at a City in masters this weekend. Black Kyurem EX seemed to be the key.
I'm 75% sure King Piplup is referring to me at Grand Rapids. Correct me if I'm wrong, because I usually am.
But I did defeat 3 Rayeels with Klinklang on the day.
My Pokemon:
4 Klink (DEX)
1 Klang (DEX)
3 Klinklang (Guess which one)
2 Darkrai EX
2 Keldeo EX
1 Mewtwo EX
1 Shaymins EX
1 Terrakion (EP)
1 Black Kyurem EX
I would assume any kind of deck that can consistently OHKO (Rayeels, Blastoise/Keldeo) would be a serious problem for Klinklang... but I won all my Rayeels matchups handily. 1st round opponent prized a Rayquaza EX, only giving him access to one, which I KO'd eventually with Darkrai. Ideally you could begin KO'd Tynamos on the 2nd turn with Terrakion or Mewtwo, but clearly that doesn't happen often.
Anyway, when you're 100% sure (and I'm mean 100%, losing a Black Kyurem EX with 4 energy is practically death for your deck) that they can't return KO your BKEX, you knock out a Rayquaza EX. And if they can't respond and you have a catcher, you can knock out another one for 4 prizes in 2 turns!
I played no switch.
Some tips
-If you have access to Tropical beach (I didn't) - play it in Klinklang
-Missing energy attachments/losing energy to KOs is your biggest problem. Do not skimp on energy, do not worry if you can keep energy on your board, this deck is capable of ludicrous comebacks
-Getting turn 2 Klingklang isn't 100% essential. You should play at least one Klang. It's important to have 2 Klingklangs up because if you lose your only one, you may end up with your energy stranded on inopportune Pokemon
-Landorus could be nice, but if you play no Switch, the chances of starting with it/getting it active turn 1 is incredibly tiny. If can be nice to do 150 to seal a win but BKEX/Keldeo/Mewtwo already does that better. In short, you shouldn't play it. Or at least you shouldn't expect it to help your eels matchup. Unless you really want to kill space and play 4 Switch, 2/3Lando and no Keldeo
-Don't even think about playing 3 Klinks
-Your prism energy are the most important piece of your deck
-Leave your energy in the best possible spots. Plan for the worst.
And no, I didn't play Crystal Wall. I probably shouldn't have even played Eviolite, literally everyone I played against had Tool Scrapper.