I find PHP the most suitable language for most projects, the R language best for data mining and machine learning (including financial data analysis), and C++ for larger, more complex projects or where speed or memory usage is an issue. I have used C++'s Standard Template Library (STL) extensively, and am familiar with C++11 and many of the Boost libraries.
Wherever possible I write code that will compile and run on both UNIX and Windows.
Most of my SQL experience has been with MySQL, Postgresql, sqlite and Microsoft SQL server; I am aware of the differences between these and other databases such as Oracle and DB2. Wherever possible I write vendor-neutral SQL.
(For human languages, English is my native tongue, my Japanese is strong (I got Japanese Proficiency Test 1-kyu in Summer 2009), and I understand basic Chinese, German and Arabic: in each case my reading/writing is notably better than my speaking/listening).