One of my favorite builds I first saw it's true potential when SlayerS_MMA showcased it in the second GSTL. It is, for good reason, overshadowed by the Hellion expand, but is not without its advantages. I really like this build on smaller maps like Xel'Naga and Shattered Temple. A lot of Zergs delay speed for a good while, so you can sometimes get a few Drone potshots off and another advantage of the build is an earlier CC than a Hellion expand would allow. In addition, you are much safer against fast Roaches because you already have the tech lab down and can scout their main for the Warren. You also stop building them after 1 or 2 and go straight into marine production with a fast stim. It is an opening that requires good multitask to keep your Reapers alive and slightly weaker to b/ling busts than the Hellion opener.
10 supply
12 rax
13 gas
15 Marine
15 OC
16 supply
16 tech lab
20 CC
After you plant your CC, start two additional raxes when you have the money, then another depot ASAP. Start stim shortly after and constant marine production. Sometimes I like to reactor a rax early when I know there's no all-in coming.
EXECUTION: Whether you build one Reaper or two, it's up to you. The job of your Reaper(s) is to scout and control the map before speed is out. The advantage of two Reapers is that they can one-shot lings. Your first Reaper can be used to scout the main base or harass the natural, it is imperative you don't lose your Reapers before your natural is properly defended with a bunker or you will be totally in the dark.
You can follow the Reaper expand up any way you want, but I love love love to follow it up with a 3rax stim push. It punishes greed and if you kept your first two Reapers alive, you will mow down any Spine Crawlers that the Zerg might have (engage them if you don't see enough units to defend). If you are able to keep the Zerg from seeing it coming, you can outright end the game or do massive damage. Don't plan on getting your marines out of there, just maximize the amount of damage you do while macroing properly; running behind the mineral lines is a great way to reduce surface area from zerglings.
IN GENERAL: This is a strong build that can lead right into a macro game, sometimes giving you an advantage. At worst you will be on even footing. It's a great reactive build to the two most common all-ins Zergs would pull on smaller maps. If you spot a Roach Warren, start Marauder production, if you spot a bling bust, build bunkers and wall them off leaving a hex off space so they don't take AOE damage. If you hold their all-in, you'll be way ahead and can probably end the game with a 4rax. If they don't all-in, you can put on some pressure, possibly get an advantage, but at the very least remain on even ground. The 3rax stim push comes at a time Zergs tend to drone up like mad. NOTE: If you spot a speedling expand (rare) before your tech lab is making, ditch this build and use the Hellion expand. Also, scout for a fast third always.
Replay: http://www.gamereplays.org/starcraft2/replays.php?game=33&show=details&id=242565
