Spoilers

Dragons of Tarkir spoilers are complete!

I will give you my favorite card out of every color that was spoiler today.

Colorless : How should I put this... in constructed formats, it all sucks.
Green : Obscuring Ather could be the card that is the key one-drop for morph decks.
Red : Kolhogan Stormsinger and Berserkers' onslaught.
Black:  Qarsi Sadist is cool in the sense that at its worst, it's two mana for two damage to target player and you gain two life.  With Burn being a prominent deck in modern, this card is not out of the question at all.
Blue: Blue cards have been mainly disappointing, so I give to you the best of what I could find,  not something that is necessarily good. Dance of the Skywise has potential as a combat trick. Cards like this end up being worth money as a rare and mythic.
White: I just love cards like Glaring Aegis for one mana. This lets you gets past a Siege rhino and let it survive one too.

This post is the one I feel least confident about, if you have any contradictions to what I wrote, please leave them in the comments.