1Rax 1Fact 1Port
From Liquipedia Starcraft 2 Wiki
An opening with 1 Barracks, Factory and Starport started before spending Vespene Gas on anything else. Previously, the standard build for fast Banshee-openings or Hellions (with a Medivac)-drop for harassment openings, but can also serve for only a fast Viking for Overlord-harass in TvZ or anti-Banshee opening in TvT to go Reactor-Hellion opening safely.
This build gives the quickest access to Starport units, namely Medivacs and Banshees that allow direct access to the opponent's base where you can aim for damaging the army size or the worker count, and delay the opponent's build to buy time. Whereas the Factory can be used for Siege Tanks or Hellions for early splash damage against the smaller army sizes.
 Basic Build Order
- Marine production can be used if the opponent has a small army size to push the opponent's base, but Hellions will be needed for Run-Bys once opponent's army production has kicked in.
- Changing the gas spending between the Factory and the Starport, there is not enough gas for both
- This is a quick tech build but still favors an expansion follow-up to better hold attacks from the ground, while Terran does not have to place as much into Missile Turrets as once would.
- Bunkers and Marines, and possibly Siege Tanks, will make up the early game defense, this can be done off a Reactor or naked Barracks, but the faster the Command Center (2) the better.
- 10 or 12 scout - confirm if the enemy is going for a fast expand.
- Starport - Finishes either move out with first Banshee or Medivac, or produce a few Hellions to poke the opposing front door.
 Adaptation and Transitions
With a lot of Tech available 1/1/1 adapts fairly well to anything you might scout your opponent doing. Except for fast expansion builds that go unpunished, 1/1/1 delays an expansion for safety, delaying additional buildings and army to match the opponent's expansion timing is recommended.
- Banshee-openings are fairly common to abuse Marine Fast Expand builds by harassing the Marines directly, causing in direct damage to the oppoent's build with forced fast tech to Starport or a bunch of Missile Turrets to defend. Attacking SCVs being a bonus in this case.
- Hellion Drop-openings for attack SCVs directly, but not common as Sniping the Medivac makes the attack a complete failure and sacrifices any Hellions still in the Medivac or inside the opposing main base.
- Viking-openings for anti-Banshee teching.
- Cloaking Field-opening were great for abusing Observers slow movement speed, not so common now, and the fact that most Protoss are blind to the Terran's opening until Robotics Facility finishes. Before Observers Protoss can poke at the opponent and count the Marines as scouting.
- Cloaking Field-opening also give rise to the infamous 1/1/1 All-In (vs. Protoss) the follows this opening with a Siege Tank and mass-Marine all-in that exploited the early blindness of Protoss.
- Rax-CC into 1/1/1 is the solid standard Opening against Zerg.
- Day9 Daily # 118 - Day Day9 and TLO talk about how awesome TLO is.
- Warden's TvP responsive 1/1/1 into general Biomech, an interesting responsive TvP guide