The A-10 Thunderbolt II (AKA A-10 Warthog) was designed around its massive GAU-8/A Avenger nose cannon.
The gun and plane were developed in parallel, which resulted in the perfect marriage. In fact, without the nose cannon, the plane is completely off balance and can't fly.
Developed by General Electric, the 30 mm hydraulically driven seven-barrel Gatling-type cannon was designed to combat tanks and provide close air support. Both the A-10 and its GAU-8/A gun entered service in 1977. This video explains the cannon's role in today's battlefield.