Pokemon with the Ability "Infiltrator" ignore Substitutes as of Gen VI. I googled, but couldn't find anyone talking about this -- isn't this a massive game-changer? Substitute, which is an utter staple of competitive battling, is now virtually useless, as the total nuke Chandelure and the ultra-high-speed Crobat both get it, not to mention the tricky-useful Malamar.
Most of the other Pokemon that get Infiltrator aren't going to be KOing or messing with anything that would be using a Sub in the first place, but still. This seems like a game-changer to me.