TvZ: 2rax *updated 8/18/2012*

This is one of the most common and basic opening builds for Terran popularized in the GSL2 by MarineKingPrime back when he was known as Foxer/Fake Boxer. This is a good build that has been used ever since because even if the Zerg knows it's coming it still has amazing potential to damage the Zerg's economy or at the very least pressure them into to making zerglings/spines. Particularly good against Zergs who choose to FE, this build can transition easily into an expand or simply more barracks if you want to attempt to outright kill the Zerg, however expanding is generally much safer.

This is the variation I have been doing:

10 supply
+11 rax
+12 rax
14 Marine
15 OC
15 supply
15 Marine
16 Marine

+ SCV production is cut for a few seconds
* Constant Marine production

EXECUTION: When to move out is entirely up to you, it can be done ASAP, but it is better to go in with 2-3 marines and 2+ SCVs, depending on the map. If you want to wall the ramp, you should start moving out with 1 Marine, or their natural expansion will finish and block the ramp with creep (assuming normal 15 hatch timing). It is IMPORTANT to rally your Barracks and watch your units, don't let drones or lings surround them and micro like a boss, even if you do not kill their natural you are not behind unless you lose every Marine without doing anything.

You will have map control until speedlings or Roaches are out. Just make sure you have a bunker and/or wall at your natural. A really sexy starting wall-off in TvZ that can be done on small ramps is walling off the bottom with your first rax and depot. This is in fact a full wall-off that denies early scouting and shuts down 6-pools. I don't know if it works on any of the current ladder maps anymore, but I used to use this on XN Caverns. (Doesn't work anymore)

IN GENERAL: This is a very strong and easy opener, still viable in the current meta, that you should absolutely know if you play Terran. The more economic version is the 12/14 rax; also good to know, but it comes out much slower. This aggressive 2rax works great on any map, though on 2-player maps I recommend proxying both raxes. If you do moderate damage to the Zerg, there is a good chance they'll try to B/ling/Roach busts or Nydus, so you must account for these no matter what, else you may let the opponent back in the game if you take too much damage.

Replay: http://www.gamereplays.org/starcraft2/replays.php?game=33&show=details&id=269799
Replay 2: http://www.gamereplays.org/starcraft2/replays.php?game=33&show=details&id=274092