I'll go down the list of decks that make me question why they weren't banned instead.

Blue Eyes MAX:

"Whats that? You don't have a 3000 ATK beater on your field? PFFT, now you do! Forget actually having to do work! Here you go! Whats that, still not happy? HERE! Have a 4000 ATK beat stick that can't be touched by anything! GUESS WHAT!!! NEED MORE BLUE EYES?!?!?! JUST RUN THREE MELODY SPELLS!!! AHAHAHAH!!!

Spellcaster/Dark Magician deck:

"Whats that? You don't have a dark magician on your field? PFFT. NOW YOU DO! Whats that? None in your hand either? HERE! Have as much as you want with one spell! Huh? Oh! He can't be touched either! None of your spellcasters can! ISN'T THAT GREAT?!??!?"

Yang-Zing:

"Whats that? You don't have 20 copies of each card in your hand? PFFT. NOW YOU DO! Just throw down a card and let it do all the work without anything having to happen to it!"

Tachyon Deck:

"Whats that? You don't have an unstoppable 3000 ATK XYZ on your field? HAHAHAHAAHAHHAHA HERE YOU GO! THANK ME LATER!"

Noble Knights (My personal favorite):

"Huh? You don't have an untouchable and super regenerative XYZ on your field who's equips keep recycling themselves? HAH!!! EASY! Here's a Medraut and an equip spell! Have fun!!"

Six Samurai:

"Whats that? You want full control over your opponents spell and trap zones without any repercussion whatsoever? Huh? You want a Naturia Beast and a Shien on your field in one turn? WHY THE FUCK DIDN'T YOU SAY SO EARLIER?! HERE! HAVE AS MANY ON THE FIELD AS YOU WANT!"

Can anyone else think of some more?

EDIT: Thanks for the downvotes on a discussion post you salty assholes. :)