Matlab is the most important one to know at my school. My probability class, my signals and system class, my pattern classification class, and many other classes use/used MATLAB projects.
Now, saying you need to be 'well-versed' is just ridiculous. You need to have a working knowledge, but it's not as if you need to code as expertly as a computer scientist. To put things in perspective, I had to take only one c++ course, which finished barely discussing what a class was.