Charon and Cerberus are the only two names from greek mythology that I recognised.
Charon being the ferryman of Hades and Cerberus being the 3 headed guard dog at the gates of Hades.
By the way, Charon is an AWESOME companion!
He's several inches taller than most humans and ghouls and within 30 seconds of hiring him, he blows someones head off (his former employer). Shame I'm a "nice" guy, he would have been a decent companion in the Wasteland.
Oh yeah, and in the Underworld clinic, there's a Ranger there who gives you a little quest which awards you with some decent combat armour as well as a new kind of hideout you can use (Reilly's Ranger compound).