Who is Mr. Gold in the movie Revolver?

From the Wikipedia page on the movie:

Sam Gold is seen to be the 'king' in this chess game of gang warfare. He is the ultimate figure that all men are supposedly aspiring to be. Sam Gold is revealed to be an ultimately powerless cipher, whose power is granted only by those who invest in him. He represents ego and self-investment. He is the personification of greed

The movie isn't an analogy to chess. The movie is about the illusion that imprisons every one of us.

Deep beneath the films violence, blood and grit, lurks a spiritual and enlightening message - a message echoed throughout time by revered figures such as Buddha and Bodhidharma, a message also echoed in Kabbalah (which is probably where Guy Ritchie drew his inspiration from, as his then-wife, Madonna, is heavily into Kabbalah). And that message is this: we are not our ego; the ego, far from being our friend, is responsible for most of our pain and misery; the ego is a product of the mind and creates the illusion of separation, the ego is a prison, a prison that very few people recognise as such.

To answer your question: Mr. Gold is everyone's ego. In Jake's case, Mr. Gold is the part of Jake who wants to kill Macha.

I don't believe there is any need for opinions or personal experiences when they say explain it quite clear in the movie. The last clip is from director himself telling you who Sam Gold is. Here is a clip from the tube

Chess is a representation of Life and Choices we make. From 0:28 to 0:49 Andre references "someone"(who), then goes back to talking about "the game" of chess.

Now here at 1:42

He's talking about an "opponent"(who) then references a "Snake"?? If you know who is usually referenced as a snake you'll have your answer. But, heres another clip that should clear it up. At 0:44 if you listen closely he is referencing "someone" again that isn't you. Hopefully these clips will help you make sense of it directly without all the shooting/violence to distract you. Once you understand the "source" of your pain you will know who Sam Gold is. Direct answer to your questions from Director of movie and Statham

As others have stated, Sam Gold is ego personified; Avi states this in the film.

The "Sam Gold" that the gangsters refer to is a ghost story created by Zack and Avi, a fiction to intimidate and threaten the gangsters' egos. Zack & Avi hired Lily Walker so that they could interface with the criminal underworld (& manipulate Macha) while remaining under the radar.

In our world, Sam Gold is literally the executive producer of the film. The first words that appear on screen before anything else are "Samuel Goldwyn."

Sam Gold is the Demiurge. A greek/Gnostic term for the insane "god" who runs this slice of the universe. It is the god of the old testament. Not the Heavenly Father that JC speaks of. A piece of "Gold" lives within each one of us... it is not our friend and it prevents us from ascending the Kabala Tree, so we may reunite with the One True God of Love.

Jake Green is the desciple of his two friends from prison who is an avid learner of their teachings about gaming and cons specific to gambling. His love of money is his egotistical prison and once he is faced with death and being penniless, reaches his full potential and recognizes his shortcomings being his ego alterself. Now Jake becomes in power of his consciousness and Sam Gold has no power over him not via Jake not via Macha and Macha sees Jake's fearlessness and has conceded to being defeated and does not accept living in such a world so he shoots his own consciousness.

Mr Gold represents Satan. Pure and simple. Satan means "in your place with something to say". He speaks to us in such a suttle way that we think it's our own voice however it's not. I love this movie!

I think only a few of you understand the movie. Same Gold is your Id/Ego. (Sam Gold/Ego sees everything but no one sees Gold.) Most people don't realize there is a difference between themselves and their ego and therefore they are constantly manipulated but their ego (that voice in your head) convincing you that it is you. The con is based on this concept that since that is the case you can manipulate anyone or everyone by manipulating their ego/id and not the person because their ego/id would do the rest my manipulating the person from within. The ultimate con because everyone trusts their ego/id because you think it is you. The last three minute of the movie lay it all out.

A lot of valid points. I've pondered most of them myself. Hell, after one late night/early morning viewing, I even considered the "Fight Club" theory. Mr Gold, is indeed ego personified. But.....What if Avi and Zach are all in Mr Greens head and he's really certifiable. Since Macha basically killed his brothers wife and daughter and set him up, it made Jake start plotting. He was "paying" Avi and Zach (aka himself) to basically further the cause and extract revenge against Macha. Idk, it's out there but it was a interesting concept to explore. Lol.