I know there are tougher NPCs in the Fallout world, but this dude is a handful. He's a fairly tough fight for an unarmored old guy, but what I found so compelling about his story is the fact that he just basically does whatever the hell he wants. Slips away from the besieged HELIOS One without being caught by NCR. Goes to the Big MT and hacks the Think Tank, fries 8's voice module, experiments on ghouls within spitting distance of the Dome, foils his own attempted assassination, modifies two highly advanced weapons with a pile of scrap metal, and then escapes by stealing a TRAIN (!) while crashing the others as a diversionary tactic. Finds and enters the Sierra Madre, whose existence isn't even believed by many, and damn near creates his own empire using technology that would seem mythical to many wasteland inhabitants.

He has joined Ulysses and JG in my pantheon of [censored] NV characters.

Elijah is my favorite villain in Fallout New Vegas. Ulysses is probably my favorite conflict character, but I don't consider him an antagonist.

Agreed.

He may be overwhelmed by greed, but he makes a lot of good points, and he's a really interesting and well-developed character.