Green beret
U.S. Special Forces wear the green beret as a distinction of excellence and uniqueness within the Army.
Green Lantern Corps
"The Corpse" is an elite, top-secret Black Ops division of the Green Lantern Corps. Members of The Corpse are not restricted by the same rules that regular Lanterns follow, and they perform the darkest, most dangerous missions and are allowed to use lethal force. These members do not use Power Rings; instead, they swallow special coin-like disks that give them all of the powers of the standard ring with a charge that lasts five earth days. These disks produce purple energy instead of the traditional green. Members of the "Corpse" do not wear Green Lantern uniforms, or display the Green Lantern symbol. Instead, they seem to prefer black uniforms that have no symbol.