The little mini XLRs made by Switchcraft and the like are sometimes used for headphone connections, like in the case of AKG. They're nice because they lock in place, and you can get a four pin version for balanced connections.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.m-s-v.eu%2Febizz%2Fsh%2Fimg_g%2Fxfk-mini.jpg&hash=bc94ceb9d6b521feea9ca39b3a0633d83a02289c)