The Assasin Suit is one of the best suits of armor you can get in the Dead Money DLC. It can be acquired in the Medical Clinic, located in the Medical District of the Sierra Madre in the Dead Money DLC.

Quick tips before you go to grab the armor:

• Dead Money DLC required. In order to get this armor, you’ll need the Dead Money DLC installed.
• Beware of security holograms. This is likely to be one of the first places you visit during the Dead Money DLC. Beware that there are security holograms in this place, which you cannot kill in a regular way. For the purposes of the tutorial, you can simply sneak past them.

Acquisition

First, follow the quest marker of the “Find Collar 12: Christine” quest, which you get at the start of the DLC. 

This quest marker will lead you to the Clinic, located inside of the Medical District.

In this area, locate a small, cyan door. That door will lead you into the clinic. Go inside.

Inside, you’ll find yourself in a lobby with a door to the left (stairs up), in front of you (bathrooms), and to the right (surgical rooms). Head through the door on the right.

Right around the corner, take the first door on your left. You’ll find yourself in a surgical room.

In this surgical room, you’ll see an operating table on the left side of the room. The Assassin Suit will be lying on the operating table.

Usage

The Assassin Suit is an integral part of your Dead Money kit. It provides very good protection (DT14), a  +10 bonus to Sneak, and has a very respectable durability of 500. It is also Light Armor, which means it doesn’t slow you down in any way and allows you to benefit from perks such as Travel Light and Light Touch.

To put this into perspective, Combat Armor, which is considered Medium armor, has a DT of 15 and durability of 400, making the Assasin Suit a much better option in the vast majority of scenarios.

Gameplay Tips

• Try to conserve the armor’s durability. Unless you have the Jury Rigging perk, it can only be repaired using Combat Armor (which cannot be found in this DLC).
• Other than the Stealth Suit Mk. II, this is the best stealth armor in the game. Thanks to its easy acquisition in the (canonically) first DLC, you should be able to acquire and use this armor very early into your playthrough.