UH-1P
An unknown number of UH-1Fs were modified to UH-1P configuration by the USAF for use by the their 20th Special Operations Squadron, The Green Hornets, based in southeast Asia during the Vietnam War.
Official USAF sources state that these aircraft were used for a classified psychological warfare role, but this is incorrect. The "Papa" Hueys were in fact modified and employed as gunships armed with machine guns and rocket launchers.
Read more about this topic: Bell UH-1 Iroquois Variants