I know some Chinese, having worked in China for a number of years. Maybe Japanese will be easier for me. By banking, I meant that since I intend to do investment banking, either on the business side or as a legal counsel, I hope to learn a language that will help me most in the career. Since Germany is the 3rd largest economy, and Japan second, Japanese and German seem like idea languages. I don't know what French is good for in the financial world, UN has 6 official languages, English, Russian, French, Chinese, Arabic, Spanish. The office of secretary general I believe uses French or English.
I think the obvious answer is either Spanish, which would be incredibly beneficial throughout most of the South and West. Or, if you are more of an international trade/business type, it has to be either Portugese (Brazil is on the verge of becoming a large international player) or Mandarin (China is about to bypass USA as the major world player) in about 20-50 years.