We all know him, the G-Man, a man of mystery in the Half-Life series. He appears in the random-most places, yet he is never afraid and never gets harmed with a scratch. It makes you wonder who he really is and where he comes from. In the first Half-Life, it appeared as thogh he was an agent of a super-secret gov't agency, but now, in Half-Life 2, all gov'ts are gone, or oppressed by the combine authority, and yet the G-Man is still as powerful as ever; maybe even more.

It makes you think and wonder about the trew intentions of the G-man, about who, or possibly what, he is. He currently appear as though he gains profit from gordon, using him as a pawn that he rents out to "employers" when profit is well enough. But what if theres more to the G-Man that the plot has yet to hint. It is my belief that the G-Man comes from the future, simply thraversing time, mingling with events that cause chaos for thousands, or perhaps he is from a future were man has teamed up with unknown aliens, to which the G-man traverses time to play into events that make the future of man stronger, or even worse.

My "Time traveling" theory, i belive is most plausable. I bet Half-Life 3 might include a little time traveling for a sci-fi twist.

I hypothesize that the entire HL1 and HL2 experience is a virtual reality training session for Gordon Freeman, who really is an MIT physicist. The program gives him combat experience because the government needs him to become an elite soldier also.

GMan is actually a guide program (kinda like Agent Smith in "The Matrix"). He gets loaded with Gordon to each of the training sessions, and set up traps and obstacles for Gordon to confront.

He has nothing to fear because he is just a program and cannot be killed. He also has the insight that the whole experience is just a series of electrical input into Gordon's neural network, and Gordon is actually strapped in a lab.

My theory is this: the G-Man is from a time far into the future, when time travel has become not only possible but profitable; companies or governments ("employers") interested in immediately bettering their respective situations ask the G-Man to alter the past in such a way that would benefit them.

This is the only answer that makes sense to me. All world governments have been destroyed, and all free-minded humans presumably stripped of any administrative or financial power under the Combine regime; the G-Man intended for you to destroy Breen, the Combine, and Nihilianth, and so could not possibly be working for any of them - and yet, he also wanted Black Mesa to happen. Think about it: in both HL1 and HL2, he watches you every step of the way, guiding, in part, your steps (as shown by his speaking to your fellow Resistance members). The G-Man, for whatever reason, wants to shape the future; as in many ways he is powerless to do so himself, he uses you as a tool, bringing you in and out of conciousness to do his bidding - which of course is ironic, as you, Freeman, believe you are exercising your free will in defeating the Combine.

Also, an interesting tidbit: the Combine works for Breen. In the Nova Prospekt level, I think, you hear him berating some Combine administrator for not capturing Freeman, and thus failing to prove their worthiness, or something to that extent.