[W0lf]

Discrete mathematics and all sorts of its application in real-world (software development) related problems. Also how any given solution to a problem in one problem domain can be transferred to a problem in another unrelated domain. Think Galois theory but waaaay less fancy :-)

[philjohn]

When I did Mathematics A-Level's, we had to select four modules. I chose pure 1, pure 2, stats 1 and, new that year, discrete 1.

So many useful groundings in various super important comp sci concepts.