Konami recently shared that a much requested feature by MGO2 players will be added in a future update, knives. The stun knife in Metal Gear Online during the time its second iteration was active, 2008-2012, was a one-hit-kill weapon both loved and hated by players at the time.
The knife is being planned to be available to all three classes, as well as attackers in Cloak and Dagger missions. The gameplay will remain largely the same from previous versions, with a combo attack and one-hit-kill stab. Most likely the animation for the stab will not be something players can cancel like they were by item switching in MGO2.