The Galaxy S6 Active is a rugged-version of the Galaxy S6. It uses the same 5.1" QHD (2560x1440, 577ppi) Super AMOLED display, but adds IP-68 dustproofing and water and shock resistance (up to 30 minutes in 1.5 meters). Other specifications include a 64-bit Octa-core CPU, 32GB of storage, 16 mp camera and a 3,500 mAh battery.
The S6 Active is exclusive (in the US at least) for AT&T and costs $499 unlocked.
5.1" QHD Super AMOLED