I'd use a Gau-8, 30MM 11 inch long cannon rounds at 4,200 rounds per minute. Just the sound would scare them, then again they would laugh because "It sounds like a person farting" Yeah, just wait to you see what the forget it does to damn tanks

Impacts on a tank during the 80's or 90's

Just to show you why the A-10 "Warthog" is the only plane that can have this mounted...