So the question is in the title:
Is there any deck that can (in the very best case) win in turn 1?
It should not be tournament legal, it should not be legacy legal, but it should follow the basic deckbuilding rules:
Constructed decks must contain a minimum of sixty cards. There is no maximum deck size; however, you must be able to shuffle your deck with no assistance. If a player wishes to use a sideboard, it must have fifteen or less cards.
With the exception of basic land cards, a player’s combined deck and sideboard may not contain more than four of any individual card, counted by its English card title equivalent. All cards named Plains, Island, Swamp, Mountain, and Forest are basic.
Without the second limitation a deck of 15x Black Lotus and 45x Ancestral Recall would possibly be a turn 1 win deck:
- 15x Lotuses would give you 45 blue mana to cast 45 Ancestral Recalls
- 45 Ancestral Recalls can force you or your opponent to draw up to 135 cards
- if you start with 6 cards(after mulligan), you have 54 left in the library, so you would want to use 18 Ancestral Recalls on yourself to get all you library in your hand
- Then you can just mill your opponent to death
But, unfortunately, this deck is just not legal. Nowhere.
Without the first limitation the following deck would potentially be a turn 1 win deck:
- 2x Laboratory Maniac
- 4x Black Lotus
- 2x Ancestral Recall
So here's how it would work:
- You will certainly have 1x Maniac, 3x Lotus and 1x Recall in your hand when you start.
- Play 2x Lotus, Maniac and Recall on yourself which will result to forcing yourself to draw cards while you can't. This would make you lose the game, but Laboratory Maniac's ability would trigger and you would win the game instead.
But again, this deck is not legal either.
The only deck that I can think of that's capable of turn 1 win with these conditions is:
- 3x Black Lotus
- 4x Ancestral Recall
- 4x Fluctuator (for higher chance of getting it earlier)
- 1x Laboratory Maniac
- 48x cards with Cycling
In best case you would get Fluctuator, 3x Black Lotus and 3x Ancestral Recall as your starting hand. Then you could:
- Play 3x Black Lotus for 9 blue mana (9 {U} in mana pool)
- Play 3x Ancestral Recall targeting yourself (6 {U})
- Play Fluctuator (4 {U})
- Play last Ancestral Recall (3 {U})
- Cycle like crazy(since you have Fluctuator all your cycles are free)
- After drawing the last card cast Laboratory Maniac (0 mana left)
- Cycle again
- Win
Is there any other deck that could possibly win in turn 1?