A second-language can lead to a wide variety of career opportunities in government, business, education, travel, publishing... Here is a list of just of few of them.
Teaching
International Law
Translation
Publishing
Immigration
Communication
Public Relations
Research
Journalism
Editing
Tourism
Movie Dubbing
Broadcasting
Speech Therapy
Law
Civil Service
Administration
Foreign Service
Diplomatic Service
Public Policy
The following website may also be useful in researching potential career opportunities for French in particular.
French for the Future website