Hearthpwn

Link to the full guide

All-In Druid is an aggro deck which aims to swarm the board from the very early turns, then make the board hard to deal with thanks to mass buffs (Power of the Wild, Soul of the Forest, Argus) or simply overrun the opponent with Savage Roar.

It relies on its starting hand a lot, because without Innervate or a bunch of one drops the deck kind of falls apart pretty quickly. This makes the deck not very consistant, although it might catch people off guard since nobody expects Aggro Druid.

When it works, the deck is super fun to play. You can get pretty sick openings with Innervate and the various buff spells and it's not too uncommon to play Savage Roar for +10 damage on turn four or five. You either win in the first turns of the game, or you basically lose since the deck has no comeback mechanisms and the card quality is overall pretty low.

Wrath is in there for the cycle, because there aren't many ways to draw cards in the deck, but if need be it can also be used to clear the board of a taunt or a troublesome minion. 

Runic Egg's deathrattle can be triggered with abusive, mark of the wild, power of the wild, savage roar and argus. That's 10 enablers, which makes sure that you'll almost always have one when you need it. 

Upgrading the deck:

Living Roots is two minions in one card for the measly cost of 1 mana, which is awesome. Makes your early game buffs a lot more powerful and if drawn late can also be used as removal or reach. Probably the most important card to add.

Mark of Y'Shaarj is usually better than Mark of the Wild, since the taunt is mostly irrelevant but the card draw (if played on Raven or the 3/2 Panther) is definitely not. You can also run both.

Dragon Egg is a better egg than the one we have, since it generates immediate board presence when hit and can spawn multiple whelps. It is found in the 3rd Wing of BRM, which is sadly not cheap to get. 

Leeroy Jenkins is a great finisher for this kind of deck.