The A-10 Thunderbolt has 2 confirmed air-to-air kills with it's GAU-8 Avenger 30mm. Both during Desert Storm.
On February 6, 1991, Captain Robert Swain shot down an Iraqi helicopter with the 30mm over Kuwait when other methods failed.
On February 15, 1991, Captain Todd Sheehy downed another Iraqi Mi-8 helicopter with the 30mm