“Wake up in the Mojave Wasteland with an edge. Courier’s Stash™ gives players immediate access to four content bundles previously available only through pre-ordering Fallout: New Vegas®. The Caravan Pack, Classic Pack, Mercenary Pack and Tribal Pack each offer unique weapons, apparel and aid advantages that will help you throughout your journey.”— Official description
It is a compilation of the four item packs that were previously released as bonuses for pre-ordering the game at certain retailers. It used to cost $1.99 (£1.23), but now costs $0.49 (£0.32). When they existed, it could have been bought for 160 Microsoft Points. It contains multiple new weapons, armors, and a supply of aid items, such as Stimpaks and Doctor's Bags.
Any file that you have will automatically add it to your pack when loaded, if you have already downloaded it.
Downloading this while playing any of the add-ons will still add the items to your inventory.
The items given to the player are relatively good for early levels, but are surpassed by better weapons later in the game. Even so, players should not underestimate these items, as they can give a great push early on in the game.