A best bet is the BoxWave Samsung Galaxy S3 DuoSuit in Super Blue (pictured) for $11.70 before the above coupon, $1.70 after. With $2.25 for shipping, that's the lowest total price we could find by $19. This slim-fitting case features an anti-slip grip, and more.
Update: These items do not qualify for Amazon Prime shipping. The information above has been adjusted to correct for this error.