The Cosmic Cube is one of those objects floating around the Marvel Universe that basically serves as a sort of super MacGuffin. It pops up occasionally to be coveted and pursued by villainous types with plans of universal domination, then disappears for awhile. It's basically an all powerful item that allows the wielder to control and reshape reality in virtually any way imaginable.
Last I checked, the Cosmic Cube was in the posession of the Red Skull in the comics, but it's been awhile since I read anything Captain America related. We've known for awhile that the Cube would be appearing in Captain America: The First Avenger as an item again coveted by Cap's arch-nemesis. Supposedly the Cube's presence will be felt in all of the upcoming Marvel flicks, but now we're getting our first glimpse of it in the posession of the Red Skull, as portrayed by Hugo Weaving. Check out the pic below!
Looks like a block of friggin' ice, and judging by the look on Weaving's face I bet he's about to say something super campy and villainy like "I now posesses the most powerful weapon in all the universe!! No one can stop me!!" just moments before Cap's shield knocks the Cube out of his hand or something. You know I'm right.
The image comes courtesy of the latest issue of SFX, but it was BleedingCool that first brought it to my attention. Thanks, gang!