With the Pro Tour looming, I wanted to throw out a dark horse spec that I'm personally intrigued by. There has been a lot of attention focused on the other engine cards in Kaladesh, such as Aetherworks Marvel, Panharmonicon, and Metallurgic Summonings, though I feel like Dynavolt Tower has yet to be given its due.
Energy is basically mana that you can pool in the vein of Upwelling without having to play a do-nothing enchantment, and the Pro Tour is very likely to showcase some degenerate energy shenanigans that we have not seen to this point. Dynavolt Tower's ability to generate "free" damage as you churn out instants and sorceries is very powerful given enough time, and my experience with the current Standard format leads me to believe that a good shell for this deck exists.
Dynavolt Tower is basically bulk, and you can find plenty of copies for fifty cents currently. It lends itself well to playing with blue cards, and personally I believe that Take Inventory is among the most underrated cards in Standard and that Ceremonious Rejection may be the most powerful sideboard option in the format. As a regular rare with a niche role, Dynavolt Tower doesn't have a super high ceiling, though you can easily double or triple up here with some camera time this weekend.