Shapka

Shapkas are a type of headgear that was secretly released during the 12/15/10 Content Update. It was first featured as a special event item in the Scorpions vs. Spider event.

Overview
Its description seems to hint that it will give a Speed, Sprint Stamina, and defensive boost, similar to the Force Recon Helmet.

It can be bought from the Black Market for a price of

Trivia

 * 183088_10150096363792066_122899437065_6680488_4717785_n-1-.jpg hat originates from Russia, as evidenced by the fact that the "Hammer & Sickle" is depicted on it.
 * Oddly enough Shapka is a more broad term for a fur hat, yet it has obvious Soviet elements, it would be more appropriate to call it an ushanka.
 * This combined with the Red Nose or Tactical Mask would give an extraordinary 65% stamina boost. This setup gives the most amount of sprint stamina than any other.