Gungeon Ant

 is a gun that alternates between firing spreads of bullets that leave behind oil and ones that burn enemies and ignite oil upon reloading.

Trivia

 * This gun is a reference to the real-life Bullet Ant. Known for its extremely painful sting, victims have likened it to "being shot".
 * The synergy is a reference to Earthworm Jim, specifically The Evil Queen Pulsating, Bloated, Festering, Sweaty, Pus-filled, Malformed, Slug-for-a-Butt.