Gotham: http://bit.ly/TmvDxU

Don't think it's Gotham, more Avenir to me, except /S (which could comes from Futura) and/M.

I knew I had already seen this. Previously asked here but still unresolved. I've found meanwhile the sample origin, a poster by Mark Owens (lifeofthemind.net?) for the Poster Issue of Korean Graphic Magazine. I've found also a better sample here. Looks definitely like a mix of Futura (/L, /D, /U, /E with middle bar lowered and /S) and Avenir (/M with vertex reworked, /C, /G with horizontal bar lowered, /A and /R).
You might like Brown.

Thank you all very much for helping me, I guess this one is really hard to solve...

And you are right Ryuk, I really like Brown!