Chinese Stealth Armor is a rare armor in Fallout New Vegas that will make you nearly invisible to enemies (although not fully, as in Fallout 3). If you steal or sneak a lot (who doesn't?) watch this video for a guide to acquiring two suits of Chinese Stealth Armor.
From the Creator:
2 suits of Chinese stealth armor can only be found on the office level of Hoover Dam. It is located in a room with radioactive barrels, in a crate against the back wall. Its existence is hinted at on the only accessible terminal on the same level.