The GAU-8 30x173mm Cannon is a large 7 barrel rotary cannon. It combines powerful ammunition with a high rate of fire, but this also means it suffers from very powerful recoil. In addition, the weapon will overheat rapidly during sustained fire.
This is the weapon which the A-10 Thunderbolt II, commonly known as the "Warthog", was constructed around. For less specialized aircraft, the hidden version of the Vulcan rotary cannon is often a more prudent choice.