The Bayonet is a cosmetic knife available to csgosk

The Bayonet is a cosmetic knife available to players in Counter-Strike: Global Offensive, and is an extremely rare item received from opening certain weapons cases.CSGO Skins The Bayonet is one of the five original cosmetic knives introduced in the Arms Deal update.

“Relatively unchanged in its design since World War II, the bayonet still retains a place in modern military strategy. Bayonet charges have continued to be effective as recently as the second Gulf War and the war in Afghanistan.”―Official description

Overview

The Bayonet is cosmetic only, and shares the same performance as the default knife.

Trivia

The Bayonet was first seen in the beta versions of Global Offensive as the default knife for the Counter-Terrorists.
The Bayonet is based on the real-life Smith and Wesson SW1B, a knife designed after the original real-life M9 bayonet.
The in-game M9 Bayonet is instead based on a more modern knife, designed after the M9 Bayonet but features a serrated blade, and is only named after the M9 Bayonet.

CSGOSK Bayonet Skins On Sale from http://www.csgosk.com/item-Bayonet.html