Green Blue Berserk
This deck has a simple plan, play a small creature or two, preferably with flying, and then use pump spells to end the opponent in just a few attack steps. The creatures of choice is first of all Scryb Sprite and Flying Men but as eight creatures isn't enough the deck often play Argothian Pixies and sometimes Serendib Efreet.
To make these small creatures able kill as fast as possible the deck uses cards like Pendelhaven, Giant Growth, Unstable Mutation and most importantly Berserk. The deck needs a lot of mana to be able to play all the pump in a single turn and sometimes also have mana for some protection so it's essential to play mana dorks like Birds of Paradise and Llanowar Elves. And one should not forget that even the 0-powered bird can act as an attacker because of all the pump spells.
Other cards that can be used are Psionic Blast for some reach, Avoid Fate for protection and Concordant Crossroads for more speed and as an answer to The Abyss.
And last but not least a fun little fact is that this is the deck that Magic's lead designer Mark Rosewater played at the very first World Championship in 1994.