Ok, this doesn't fit exactly the Ubers ladder, considering it's a random Wi Fi, but I used an Ubers team, and trust me, this story deserves to be told.
So, I was looking for people to test on my fresh EVed sun team, when I notice a weird profile. His nick was the same symbol (maybe a Kanji) repeated, all his datas were numbers with question marks, and he had no pokémon shown.
I immediately felt like he was a cheater, and challenged him to see what crazy shit he would have shown. And oh boy, was it a trip.
I kinda defended my self (put down three of those things), but though my ass was kicked, I regret nothing. Every single turn was a majestic WTF.
-Shiny Bulbasaur called Heatran, doing the sound of Deoxys, using Stealth Rock, Spikes, and Thunder Wave.
-An EGG with Trick Room, Sheer Cold, and what I assume is No Guard as ability.
-Shiny Volcanion using Draco Meteor, and packed with Contrary. Also, he hade the water jem.
-Shiny Mega Mewtwo Y. And I'm not saying that he evolved regular Mewtwo. HE LITERALLY SENDS IN MEGA MOTHERF*CKING MEWTWO Y.
AND THE NEXT TURN HE EVOLVED INTO THE X VERSION.
And yeah, he had Sheer Cold+No Guard.
At this point I lost. And he didn't even show Yveltal and one of the Mega Lati.
Seriously, never before I had such a mindf*ck.