High-explosive anti-tank warhead

The high-explosive anti-tank warhead, also known as 85mm HE, 85mm HEAT, or just HEAT, is a shaped-charge that was invented during World War II. As the name implies, it was meant to be used as an anti-tank round. Notable weapons to use this type of ammo are the RPG-7.

Soviet Union
During the Virtuous Mission and Operation Snake Eater, various KGB and GRU soldiers, respectively, utilized HEAT rounds for the RPG-7.

America
Aside from Naked Snake utilizing HEAT ammo during Operation Snake Eater (most notably using it to save Ocelot from collapsing debris as well as to fight the Shagohod), various soldiers led by Gene occasionally used them during an alert during the San Hieronymo Incident. In addition, the Intercontinental Ballistic Metal Gear was to have utilized HEAT rounds via a recoilless cannon upon completion, as discovered by Naked Snake when investigating the cargo.

Peace Sentinel as well as Soviet soldiers utilized these rounds due to using the RPG-7. The MSF also utilized these rounds after procuring the weapons themselves.

Middle East
During the 2014 Guns of the Patriots Incident, the Middle Eastern militiamen, largely due to lacking much funding, utilized HEAT rounds due to using RPG-7s.