Each week, one randomly-chosen member of the Gears of War: Judgment
community will wear a special multiplayer skin called the Epic Reaper – yet the ghoul is more than just a skin. The Epic Reaper has "special abilities and physics" that will make him (her? it
?) "not very easy to kill," this Epic blog post
In addition to the skin and whatever these special properties are, selected Reapers will get custom dog tags – everyone who kills a Reaper will unlock a special medal and weapon skin. Epic employees will also have the skin in multiplayer after launch on March 19, so if you can take one of them down, you'll get the medal and skin.
The only thing Epic Games is willing to share about the process of choosing Epic Reapers is that it will be "based on their contributions to the community." If you want to nominate someone to be chosen, you can do it on Twitter just like every other contest nowadays.