Done a wonder run when starting the game (basically a softer version of a Wonderlocke run, same rules but without the fainting = dead part) and got some surprisingly good trades which I kind of felt guilty about.
Most of them were obviously IV breeding cast offs but my little group consisted of and evolved to:
Riolu>Lucario
Espurr>Meowstic
Larvitar>Tyranitar
Froake>Geninja
Charmander>Charizard
Chespin>Chesnaught
Since I'm a roleplayer at heart, thought up a little backstory of being a trainer that went around taking in the pokemon nobody wanted.
A rather worrying moment came when a certain someones MegaGyarados KO'd two of my little team back to back. I could picture the cheesy anime scene between the two.
"You honestly thought your team of second hand rejects could truly beat me, what chance do you think they stood against my power?"
"I'll show you that within the heart of every pokemon, burns the soul of a champion!"
At which point I send out Lucario, megaevolve it and it KOs MegaGyarados in one use of Close Combat.
That team also went end to pretty much sweep the Elite Four and the Champion with none of them getting KO'd.
Pretty good for a bunch of mons nobody thought worthy of keeping.
Now I've done that, I've settled down and now breeding Goomy, so effectively retired. Makes for an interesting RPers story in my head anyway.