've written about a deck like this in the past, but Gertjan Schreur sent in a decklist that accurately points out that the BUG Skirsdag High Priest shell got much better with the printing of Varolz, the Scar-Striped.
The interaction between undying green creatures with Rapid Hybridization and Skirsdag High Priest was already good enough to win some tournaments, and Varolz, the Scar-Striped is exactly what this deck needed.
To me, the best card blue offers is Rapid Hybridization, but Snapcaster Mage and Evil Twin are both quite respectable, and it's always nice to have access to countermagic.
The deck featured is the deck as Gertjan Schreur submitted it, but I'd definitely make some changes.
I'd start by lowering the curve—I don't like Thragtusks in the main deck of a deck with twenty-two lands. I'd cut them for the fourth Young Wolf and the fourth Rapid Hybridization, since that's really the point of the deck to me.
I'd look to further lower the curve and cut some combination of Evil Twin and Soul Ransom, both of which I think are a little better in the sideboard, and I'd probably play Experiment One. This deck was submitted without a sideboard, so the sideboard is my own suggestions. The sideboard is what I would play with my version of the main deck, just to avoid using sideboard slots on the fourth Young Wolf and Rapid Hybridization.
Gertjan Schreur's BUG Varolz
Sam Black is a Platinum Pro Player and longtime writer for StarCityGames.com. He is a respected deck builder and took over Daily Decks for the first half of 2013. If you have an original deck you'd like to see featured, email him with the link above.