SPIPS Software
During more than 30 years of my career I've learned, used and sometimes taught a number of operating systems and programming languages. From 1997 and on I've mainly used Gnu/Linux unless forced to use something else.
My favorite tool kit consists of C, Tcl/Tk, Vim, (La)Tex, Maple (not necessary in that order), but FORTRAN, LISP, Matlab and C++ are also fine with me. I prefer gcc and make but can also use MS Visual Studio.