Languages
I can already communicate at a reasonable level (I'm a native English speaker) or am currently learning the languages I'm really interested in. I speak Chinese ( intermediate level), Russian (at an elementary level), Spanish (intermediate level) and recently started learning Arabic ( which will take me a lifetime because I self learn languages and Arabic is ridiculously difficult to read). So first I'll like to get to an advanced level in all those languages first, although I'll use this one time opportunity for Arabic. These languages meets my needs and interests:
Chinese: native culture, history and the Chinese influence in the economy and international relations, Asian Medicine and ancient philosophy.
Spanish: The amazing sounds of the language, Spanish and Latin American culture history, being able to travel to South America, communicate with 400+ million native speakers and Spanish literature is awesome. I'm also really interested in international development for which Spanish is useful language.
Russian: Central Asian native cultural roots, interest in minority politics and identity self-determination in former Soviet Union states, as well as the influence of Russia and Central Asia (there are enormous reserves of oil, gas and renewable resources in that region) in international relations. Central Asia is also a beautiful region (although there's a bit of political instability at this point in time).
Arabic: The opportunity to access and better understand middle eastern history and Islamic history. The language script looks beautiful as well.
If time wasn't an issue, I'd love to be able to read Latin and Sanskrit (ancient languages are supposed to be read not spoken). I find the ancient world fascinating, especially Roman history and Indian philosophy. In terms of spoken languages, probably Japanese because of the art, food, culture, history of the Meiji restoration and the advanced scientific research conducted by Japanese universities (most of the research papers are publish in Japanese Scientific Journals). German is also interesting (it looks really cool), but I wouldn't use the potion for that since it's a relatively straightforward language to pick up. Mainly for the classical music (Bach, Strauss, Wagner) philosophy (Marx, Kant, Nietzsche), Science (Einstein and the focus on scientific research in German universities) and I really love Vienna.