An airplane meant for a single purpose.
Once you have air superiority then you need an effective way to attack ground targets. Missiles are expensive. Fighters are only lightly armored, vulnerable to ground fire and very expensive to replace. Also to hit ground targets accurately you need an airplane that is not moving too fast, and to take out armored targets (like tanks) you need a big gun.
The outfit below clearly takes pride in their equipment.
The emblem on the front of the gun says “Peace through superior firepower”.
Note: Original sites are gone for the above images.