GA-KO

A duck seen as taking a proud pose. It makes an appearance in many Metal Gear Solid games.

Metal Gear Solid 3
In Metal Gear Solid 3, when Snake obtains the GA-KO Camo, if he calls Para-Medic, she will say that he looks "Cute". Then, she will chatise you for not knowing what GA-KO is.

Metal Gear Solid: Portable Ops (+)
In Metal Gear Solid: Portable Ops, and MPO+, GA-KO will appear as the target that needs to be captured in its iteration of MGO.

Metal Gear Online
In Metal Gear Online, the GA-KO, and sometimes the Kerotan, will need to be captured in Capture Mission, Solo Capture Mission, Rescue Mission, and the upcoming Race Mission.