The Warrior Feather is an accessory with two small red and white feathers on a small detailed disk that can be attached to Amy's hairband. With the Warrior Feather, Amy is able to perform the Spin Hammer Attack with her Piko Piko Hammer.
The Warrior Feather is located in the Egg Carrier's Adventure Field. After Gamma frees her from her prison on the Egg Carrier, Amy automatically enters a room where she has to complete a small game to escape. The game is Hedgehog Hammer, which is a parody of the Whack-a-mole game, except there are three dolls: a blue doll (Sonic) that gives 100 points, a yellow doll (Super Sonic) that gives 500 points, and a Robotnik doll that takes away 200 points. If Amy manages to beat the current high score, she will be awarded with the Warrior Feather.
The Warrior Feather is one of the two upgrades from Sonic Adventure and its remake that is not found lying on the ground, surrounded in green light, but is given automatically after clearing an event, the other being the Long Hammer.
Like the Rhythm Badge, this upgrade is needed to beat the game, but gives a move that is never required to use and is not very effective at destroying enemies.
The Warrior Feather was also called the "Fighters Feather" in the Hedgehog Hammer score screen of the original Japanese release of Sonic Adventure. It was changed to the Warrior Feather in subsequent versions.