aleb Durward has been playing the Tezzeret deck in Legacy for a long time, and he has been continually updating it while doing so. His latest iteration looks as cool as all the previous ones and includes all sorts of interesting combos and sweet one-of value cards.
The core of the deck involves Ancient Tomb, City of Traitors, and Dimir Signet or Talisman of Dominance (a portentous name if I've ever seen one), all of which work toward the goal of resolving an insane four-mana Planeswalker. With four Tezzerets and three Jaces, the deck has no shortage of power, and with six two-mana lands and six Talismans/Signets it isn't that unreasonable to turn-two a Planeswalker.
Once you have a 'walker going, you generate massive card advantage each turn, either by Brainstorming with Jace, Impulseing for artifacts with Tezzeret, or just turning random artifacts into 5/5s with Tezzeret and killing the opponent (you have all the cards if your opponent dies, right?). Both Planeswalkers also protect themselves, either by bouncing opposing creatures or by creating a wall of 5/5s, with the additional option of using Tezzeret to dig for defensive artifacts.
Speaking of defensive artifacts, this is still Legacy, and you do still need to interact with your opponent (unless you plan on winning turn two, which this deck doesn't). The first line of defense comes courtesy of Commander (2013 Edition), as Baleful Strix gives the deck a cheap and advantageous roadblock. It's also pretty nice when you get to upgrade it into a 5/5 with Tezzeret and fly over for massive damage. Chalice of the Void and Ensnaring Bridge both work to lock out opponents, either by cutting off a large portion of their spells or a large portion of their creatures, and can sometimes combine to prevent opponents from having any outs to the lock. Tezzeret is happy enough to drain the opponent to death, even if attacks aren't legal. Engineered Explosives, Ratchet Bomb, and Damnation wrap up the creature removal, all sweeping various things off the board.
There's even a combo element here, with Thopter Foundry and Sword of the Meek, supported by Transmute Artifact. Thopter-Sword is an old Extended powerhouse, giving you a 1/1 flier and 1 life for each mana you spend, which most fair decks have a very hard time beating—as do some of the unfair ones.
Even though Grand Prix Washington DC has passed by now, this is an awesome enough Legacy deck that I'd keep it in mind for any event you might be interested in playing in.
Caleb Durward's Legacy Tezzeret
Luis Scott-Vargas plays, writes, and makes videos about Magic. He has played on the Pro Tour for almost a decade, and between that and producing content for ChannelFireball, often has his hands full (of cards).