The Charted Industries of Singapore Ultimax is one of the most renowned light machine guns in the world, yet has never really been adopted to the full extent of what it was capable of. The only real military it served was the Singaporean Armed Forces. It was used by multiple other countries and agencies, but not in a full-service adoption.
Designed by none other than James Sullivan of AR15 Lore, it had a very unique recoil absorption system wherein the bolt never actually smacked into the rear of the receiver, thus creating a constant cycle of firing until the last round was fired and the bolt slammed forward into the empty chamber.