The One Man Army bag is seen in the Multiplayer of Call of Duty: Modern Warfare 2, if the Tier 1 Perk One Man Army is selected. It takes up the player's secondary weapon slot, and is selected as if switching to the secondary (Triangle on the PS3, Y on the Xbox 360, and 2 on the PC). As soon as it is selected, the HUD will read "One Man Army". The class selection screen will then appear, and after the player chooses their class, it will be switched to in the time period of five seconds (three if OMA Pro is being used). The bag will then be put away and replaced with the primary weapon of the selected class.
Render of the One Man Army Bag
The One Man Army Bag, as it appears in weapon form.
One Man Army Bag in "Stay Sharp"
A One Man Army pack is visible during the mission "S.S.D.D.", near the first intel item, by the soldiers fixing the Humvee and at the entrance of The Pit.
Written on the bottom of the bag are the words "No Scope", which refers to a player getting a kill with a sniper rifle without aiming down the sights (similarly to hip fire with other weapons).