Call of Duty: Black Ops II

To get this achievement you must purchase the new perk called "Who's Who" (Cost: 2000) but note you must turn on the power first. I found this machine in the elevator to the left of the spawn door (not beside the M14, its an immediate left). It can also be found in the elevator to the left of the PDW below the spawn (beside the window where you can see the Dragon).

Once you purchase the perk, you must down yourself and you will go into 'Ghost mode' (or as Badonkadonk115 puts it 'Limbo state'). In this mode you will have only your pistol. You must go over to where your body is and revive yourself before you bleed out. Don't worry about spawning too far away, you'll spawn fairly close to yourself going into Ghost mode. Note that you can still be attacked while in Ghost mode, so do it when there are no zombies around. You have approximately 45 seconds to perform the revive, or else you will miss out on the achievement as well as retaining all of your perks and weapons if you bought any.

*Final update to this solution Apr 15 2017. Added a video for further clarification.

You will have to purchase the new perk Who's Who which costs 2000 points. When drank, this perk will allow you to revive yourself when downed by a zombie. It will respawn you with the M1911, so I suggest doing this at the end of an early round to avoid having to fight through hoards of zombies later on. This can be done on easy.

Step 1: Turn on the Power (750 points)
-Take the elevator in the left of the spawn room let it drop down and jump across to the power building. Open the double door by the power and throw the switch to start the elevators

Step 2: Getting to the Perk (2000 points)
From power you want to take an elevator up to the roof, run up the ramp by the dragon and jump across back to the first building. The perk will be in 1 of three locations. Once you jump across it could be to the left, straight ahead or up the straight ahead elevator back at the beginning spawn floor. Drink the perk for 2000.

Step 3: Revive yourself
If you are playing solo get the last zombie in an early round (round 2 or so) and let it down you. You will respawn with the M1911 pistol. Kill the zombie then quickly revive yourself before the next round starts.
If you are playing in a group, you can have someone lead the zombie away so you can revive yourself.

Using Who's Who will allow you to keep all your other perks and pack a punched guns.

There are already good guides but i think that it´s not easy to find the perk (because it´s random) so i will give you a few tips.
If you have any suggestions leave in the comments.
Hope you found this helpful.

Collect 2,750 points in order to buy one door and get the Who's Who perk. The achievement basically consists on reviving yourself. For that you need to buy the Who's Who perk which is new on Black Ops 2 by getting on the broken elevator from the starting room, then jumping to the next building, opening the power room door, turning the power on, jumping to the elevator on the right but the one on the left and that way you will get to the rooftop.

Now that you are on the rooftop, jump to the next building and earn 2,000 points which you will invest on the perk. After getting the perk, let yourself die, go back to revive your body and the achievement will pop out.

Here is another way to do this Achievement.All you need is to locate the Who's Who Machine and get 2000 points

Follow the guide on the video below.

Just a heads up this achievement is possible to achieve on easy difficulty, making this cheevo a lot easier.