One of the first decks I ever owned was the Simic Mutology theme deck from Dissension. I really loved the way graft worked, even without any changes to the deck, and further changes only made it more nasty. So when Gatecrash came out and the Evolve mechanic was released, I've been thinking of ways to make it work. I think this deck gives both Graft and Evolve equal love and gives it a really good combo synergy to make for some easy (and awesome) wins.
The deck is very low cost (Cytoplast Root-kin being the most expensive at 2GG) and relatively cheap (most expensive cards being Breeding Pool and Voidslime, and Voidslime is not even necessary). The deck consists entirely of low-power creatures (with cool abilities that help eachother out) and instants (counterspells and combat tricks).
The idea is to use the Graft and Evolve triggers together (usually by putting the Graft trigger on the stack first) to get twice as many +1/+1 counters on creatures as you'd normally get. Then get a creature with evasion (Cloudfin Raptor or Jhessian Infiltrator) to attack, and use a combat trick (Bioshift, Simic Charm, Biomass Mutation) to make it huge and deal a bunch of damage. The counterspells and control spells (Spell Rupture, Voidslime) can be used to delay the game until you get what you want done. You can even use Bioshift as a possible removal spell (like on a hydra) should the need arise. Have fun!
Start the game with a 1 or 2 drop (Cloudfin Raptor, Jhessian Infiltrator) to get some early game damage or blocking done. When you get into your 3 drops, you got Vigean Hydropon, who's basically a warehouse for +1/+1 counters for your creatures, and Vorel of the Hull Clade, who really benefits the grafters by making them twice as big with his activated ability. Or you can use Renegade Krasis to get some real counters on your creatures. Once you have Root-kin and Krasis on the battlefield, it's only a matter of time until you have a creature big enough, or an instant, to end the game. Use your counter spells and Simic Charms to take care of big nasties your opponent throws at you. On the sideboard, you can get Simic Manipulator, to use your Root-kin/Krasis combo to just steal your opponents creatures, Crowned Ceratok, if you instead just want to trample your opponent, Trygon Predator, if an opponents artifacts/enchantments prove to be too much to handle, or just get some more Simic Charms/counterspells to help you out.
One of the many cool strategies includes Raptor, Hydropon, Vorel & Bioshift. Raptor evolves after Hydropon enters the battlefield (since it's a 5/5), so it gets a counter. It'll more than likely evolve again after Vorel comes into play. Then attack with Raptor (with 3 lands untapped), wait for your opponent to choose not to block, then cast Bioshift to place all counters from Hydropon onto Raptor, then use Vorel's ability on the Raptor to double the counters, and you just got made a 2/3 into a 12/13 flier!
It may seem like there isn't a whole lot of removal in this deck, but Cytoshape is the perfect removal card! Think about it; say you have Cytoplast Root-kin or Vigean Hydropon on the battlefield. They both have graft, so they are 0/0 creature's that enter the battlefield with counters. Simply cast Cytoshape, targeting an opponent's creature, and make him a copy of a graft creature. It becomes a 0/0 (provided it has no counters), and immediately goes into the graveyard.