It depends on what your goal is. If you want a well paid job in business area, then C# and/or Java. If you want to broaden your CS knowledge, then Lisp, Small

It depends on what your goal is. If you want a well paid job in business area, then C# and/or Java. If you want to broaden your CS knowledge, then Lisp, Smalltalk, Eiffel. If you want to work on shrink-wrap software then C++. It's worth pointing out that Bjarne Stroustrup, creator of C++, is critical of it.