While, overall, we're seeing a lot of diversity and health, particularly in Best-of-Three, we did act recently to issue a Best-of-One-only ban on Leyline of Resonance
2 Embercleave Part combat trick, part Equipment, Embercleave is a classic game-ending win condition for aggro decks, provided you can get enough creatures on the board to bring that cost right down
However the reason that Konami had to pull the trigger and place Norden on the banlist was because of how it was abused by the Zoodiac deck to create insane plays and allow the deck to have massive draw potential
When you have a Pendulum Monster in both of your Pendulum Zones, you can Pendulum Summon as many monsters from your hand that have a Level that is between the Pendulum Scales of your Pendulum Zone monsters
The Battle decks are some sort of theme deck that comes with 60 cards and that can, theoretically, be used to play off-the-self
I would say that Kitesail Freebooter was only recently dethroned with the printing of Deep-Cavern Bat (also found in an Ixalan set, conveniently), which might be the best version of this type of card ever printed