[thejynxed]

Pencil/pen, paper, flow charts, and in some cases one of those TI scientific calculators can come in real handy.

This being said, I've never gone much away from C/C++/Pascal/Assembly/COBOL/FORTRAN and various forms of BASIC where what I mentioned helps immensely (I work on legacy systems in my spare time, CS isn't my primary field), although Python, Haskell, Rust and GO have piqued my curiosity.