How to deal with 2-faced co-workers? Telling a supervisor or going to H.R. is not an option.?

It depends on what you mean by 2-faced. If it's something you can ignore I suggest you do it. Ignore him and pity him for having such a crappy life that he feels like he has to take it out on others.

If ignoring him isn't an option than you can stand up for yourself. Granted you want to do this in a very specific way. When he makes the 2-faced comment you face him and very respectfully tell him that what he said was not appropriate. After you say this I strongly recommend you remove yourself from the situation. If he tries to argue back just say, "I prefer to be done with this conversion." this method of confrontation works well because 1) you aren't being mean so he can't make an excuse for his behavior 2) by not giving into his arguing you are making him appear and feel foolish

I sympathize, I once got a rude coworker to finally stop being so rude by telling her if I looked like her I'd be a ***** too! She never bothered me again

Well Linda (I see what you did there. Clever.) You'll just have to put on your big girl pants and deal with it if you insist you can't go to HR.

I can kill em all with kindness!

Have you tried insincere sweetness?