Standard is still pretty new and fresh, but at this point we've had a couple of cores solidifying themselves as pillars of the format. One of those is the Izzet shell (either Dragons or Turns), another is the Blood in the Snow shell (either Mono-Black or with a second color), and the third, and by far the biggest, is the Esika's Chariot + Wrenn and Seven shell.
There are many different decks that play those two cards in combination, on all parts of the metagame spectrum. It's easy to see why — both cards are individually powerful and, very importantly, work on both offense and defense. If you're on the back foot, then they produce a number of very solid blockers, and if your opponent is stumbling, they can close out the game very quickly. Then, of course, there's the one-two punch of Esika's Chariot followed by Wrenn and Seven, where you make a Treefolk, use that to crew the Chariot, and then copy the Treefolk upon attacking.
Another card that combos extremely well with those two is Storm the Festival, as they are exactly the sort of permanents you'd like to put onto the battlefield for free. Together, these three cards will form the core of every deck I'm writing about today.
When Storm the Festival was first released, I sort of dismissed it as a gimmicky card — it looked too expensive for something that was sorcery-speed and just overall not worth the trouble. I believe I was wrong for two main reasons: