This is from a rather old game, but the build is still great. Polt calls it the safest opening against zerg. I haven't included all the build times for supply depots so you'll have to practice to get a feel for the timings.
14 | 0:17 | | |
16 | 0:40 | | |
16 | 0:46 | | |
19 | 1:29 | | |
20 | 1:34 | | |
20 | 1:41 | | |
20 | 1:57 | | |
21 | 2:01 | | |
21 | 2:03 | | |
23 | 2:24 | | |
25 | 2:39 | | |
26 | 2:46 | | |
26 | 2:48 | | Build some SCVs with this command center and float it only when you feel safe. |
27 | 3:08 | | |
27 | 3:15 | | Train six to eight marines depending on how safe you feel against a rush. |
32 | 3:29 | | Position this tank defensively near your main ramp on the high ground. |
37 | 3:45 | | Use this to kill overlords. |
43 | 4:00 | | When your tank finishes float your factory to a new location. When your viking finishes float the starport to the tech lab. |
50 | 4:25 | | Float your barracks and use it to build this tech lab. |
50 | 4:26 | | |
53 | 4:29 | | |
55 | 4:37 | | Build this one at the lone reactor. |
55 | 4:38 | | Build this one by itself. |
55 | 4:39 | | |
58 | 4:52 | | |
58 | 4:53 | | |
59 | 4:54 | | |
59 | 5:00 | | |
59 | 5:02 | | |
64 | 5:15 | | Float your factory to a new location at this time. |
66 | 5:27 | | Build at the lone reactor, When your second banshee finishes swap the factory with the starport and begin making medivacs. |
69 | 5:28 | | Build by itself. |
This build gets out a fast tank followed by two banshees for fending off roach/ravager aggression or even a speedling rush. It also delays marine and medivac production as well as stimpack in favor of taking a fast third base. The build is versatile enough to allow you to build tanks or liberators instead of banshees in case your opponent went hydralisks or mutalisks. You can even forgo the second reaper and the banshees if you anticipate your opponent will go for a ling/baneling all-in.
Note: At around 5:30 you will have a surplus of minerals with which you can afford to wall your natural ramp with multiple supply depots.