The USAF is currently looking at several light attack aircraft to supplement and, some hope, eventually replace the A-10 in the COIN/CAS role.
http://www.thedrive.com/the-war-zone...onal-arms-fair
Armed crop-dusters have been used quite recently in Libya by mercs flying for one of the contending political factions.
https://medium.com/war-is-boring/eri...a-88fcb8e55292