Chest of Chicken is a challenge in Sunset Gulch. It is earned by carrying the chicken to the last room/section of the area.
Where is the Chicken?[]
The chicken can be found to the left of the two flamethrowers, which are near the top of the first room/section of the area (the one you start out in). Go to the left and jump up, and, as you can see in the picture to the right (click here for a bigger version), there are steps that lead up. Go up to them, then to the left. You will drop down two steps, and there's the chicken.