Flash just got banned. I just read about the deck about a week ago. Well, the June 1st banned and restricted list just included this little bastard.
Flash deck is capable of killing the opponent on the turn zero which means that if your opponent goes first, you can kill him on his first upkeep, before the draw step.
Here is how you do it:
1) Choose to draw first. If Gemstone Caverns is in your opening hand, put it into play, removing any card from your hand.
2)Your opponent goes first. On his first upkeep, kill him. Here is how you do it. Remove your Elvish Spirit Guide or Simian Spirit Guide from your hand, adding one mana to your mana pool. Tap your Gemstone Caverns for U.
3) Cast Flash. If your opponent didn't counter Flash, you pretty much sealed the deal. Flash resolves, and put Protean Hulk into play.
4) Don't pay the reduced cost and sacrifice your Protean Hulk. Search for 4 Disciple Of The Vault and 8 zero cost 0/0 artifact creatures like Shifting Wall and Phyrexian Marauder. The artifacts die and the Disciples deals 32 damage. You win.
5) Of course, you're gonna need counterspells to back up your Flash. Since you won't have any mana, Force Of Will and Pact Of Negation are your friends.
Well, as I said, Flash just got banned, effectively June 20th. Not that it matters to me. I don't play Legacy.