A Decoy is an Assist item that can be equipped by Federation Marines in Metroid Prime: Federation Force. When used, a model of Samus Aran's upper torso is deployed to distract enemies nearby, such as Pirate Troopers and Ice Titans. A short musical cue is heard when it activates. The Decoy appears as a small scarecrow-like model that wobbles from side to side when placed on the ground, and begins to shoot at enemies until it is destroyed, or after a certain amount of time has passed. MODs can give the Decoy ice and shock properties. A demonstration of the Decoy can be viewed here: 
Samus herself appears in the game as a non-playable character.
"A deployable model of the Space Pirates' most hated foe."