World Records

The following are records that are possible or have been accomplished in Hearthstone as well as the set-up.

Please edit and enjoy.

Fastest Kill: Turn 1 one mana kill
This was accomplished by Athene and Zyker.

The planned Set-up:
Zyker was to play Innervate followed by Millhouse Manastorm, while Athene should just try to play as many powerful spells as possible.

What actually happened:
Athene's Starting Hand was Bluegill Warrior, Blessing of Might, Ysera and Lay on Hands. He rejected all except Lay on Hands, and started with 2x Lay on Hands, Avenging Wrath and Holy Wrath.

Zyker played Innervate and Millhouse Manastorm afterwards, then Athene played Lay on Hands on himself, and drew Alexstrasza, Blessing of Kings and Blessed Champion. Then, he played Lay on Hands again and drew 2x Stonetusk Boar, and a Ysera. After that, he played Avenging Wrath which destroyed the opponent's Millhouse Manastorm and dealt 4 damage to the enemy hero played Holy Wrath and drew Holy Wrath, thus dealing 5 damage to the enemy hero, played Holy Wrath again and drew Sea Giant, thus dealing 10 damage to the enemy hero (whose health was now reduced to eleven), played a Stonetusk Boar, played Blessing of Kings on it, played Blessing of Might on it, played Blessed Champion on it and used it to attack the enemy hero.

Here is the Youtube video: https://www.youtube.com/watch?v=h9YcErterxo

Most Same Legendaries on board: Theory (not accomplished yet)
We shall take the legendary as Hogger, Doom of Elwynn.

The planned set-up:
You must play this in Arena. Play a Mirror Entity and end your turn. Your opponent plays Hogger, Doom of Elwynn and ends his turn. You play on the next turn 2 Faceless Manipulators targeting Hogger, Doom of Elwynn. You end your turn. Your opponent ends his turn. You play Herald Volazj. You end your turn. Your opponent uses Hogger, Doom of Elwynn and kills your Herald Volazj. You play your own Hogger, Doom of Elwynn.

Most cards drawn in a turn: Assumed 1003
This feat was performed by HysteriA and Poxkajka.

The planned set-up (assumed):
This is an assumption, as they showed no set-up, but is easy to see how it worked somehow. There were probably 5 Lorewalker Chos on the board at some time (including the three Faceless Manipulators probably played) and the Poxkajka kept on playing Blessing of Wisdom on his V-07-TR-0N (while HysteriA played it on another target which never attacked). Then, it was probably copied at the last few moves by HysteriA's last Faceless Manipulator and attacked so that 1003 cards were drawn that turn.

Largest weapon ever: 8000/infinity attack
Practically, the largest weapon ever had infinity attack capability by HysteriA, but to save time, he only increased it to 8000 attack. There was practically no set-up.

What actually happened:
This happened in the Rafaam Unleashed encounter. HysteriA played a Blingtron 3000 which equipped a Poisoned Blade for HysteriA. On the next turn, he then played a Coldarra Drake and continued using his Hero Power, Rummage, until his weapon had 8000 attack.

Largest minion ever (Theory): infinity/infinity
See Card combinations (strategy)#Adventurer.27s dream.