Okay, a bit of a disclaimer before we get to the achievement talk. To do this one, you'll have to have bought the Old World Blues DLC for Fallout: New Vegas.
Now, in order to get the 'Cardiac Arrest' achievement, you'll have to recover the Stealth Suit Mk II from the X-13 Testing Facility. What's so special about this armor? Well, it'll improve your sneak skill by 10 points. And with each firmware upgrade to the suit, different bonuses will apply. I'm not going to list everything here, but if you check out this link, you'll see a great rundown on what makes this suit so awesome. And check out the video below to find out how to find the suit.
- Xbox 360: 20G
- PlayStation 3: Bronze trophy