This might be the Galaxy S6. It started with a few images of a phone shrouded in bubble wrap, but that was quickly followed by more images of the phone from all angles. You can never be completely sure with leaks, but these look legit.
The Galaxy S6 (if that is indeed what we're looking at) still has a very Samsung vibe with the rounded corners and physical home button. The edges appear to be metal with a very gentle rounded shape. This is obviously the standard GS6, not the rumored edge variant with the curved screen. It actually bears a passing resemblance to the iPhone 6 from the side. Also note the big camera hump on the back.
There are no pictures of the device on, which is a little odd. According to the leaker, this is an AT&T pre-production unit. It has a "Not for sale" stamp on the back and a doted pattern on the front bezel. Those dots are probably unique and will lead Samsung to the source of this leak. Just a few days until the official reveal.