Blue/White Artifact Self-Replicating.
I'm actually in love with this deck after a few runs with the finished product. If the name of this deck is any indication, it's absolutely bonkers by midgame. The main mechanic revolves around a self-sustaining factory mechanic exemplified by Mishra's Self-Replicator; however, it is further pushed to ridiculousness by Mechanized Production, which allows you to replicate enchanted artifact at the beginning of every upkeep, and if you have 8 artifacts of the same name on the field, you win. The possibilities abound:
Mishra's Self-Replicator
You could do the obvious and enchant this card, compounding its natural replication, leading to a fast win, but this card costs 5, while Mechannized Production costs 4, so you still wouldn't get that ball rolling until turn 6 or so. As such, it's far more fun to replicate these other guys.
Chief of the Foundry
This card only costs 3 and gives other artifacts 1/1. Enchant 2 of these guys to swing for over 20 by turn 5. Use Karn's ultimate to put an X/X artifact (X=# of artifacts) and all of a sudden, by turn 5, they'll be around 10/10.
Jhoira's Familiar
Historic spells now cost 1 less to cast. Ideally, you'll get this out by turn 3, so by turn 5 or 6, you're playing most of the deck for free, and the Mishra ball is rolling like crazy. Also keep in mind that this card counts towards Karn's casting cost, as he is legendary (historic).
Manalith, or Gilded Lotus
Azorius acting like a mono-green Zendikar deck lol. Put a Mechanized Production on Monolith potentially by turn 3 to put you 3 mana ahead by turn 4. Then pop a Gilded Lotus, putting you 7 or 8 mana ahead by turn 5, when you enchant Gilded Lotus, maybe put down your other Gilded Lotus.. you get it.
It may get beat by massive aggro, but if you don't break apart this factory by turn 5, good luck XD
