While not everything learned in an undergraduate computer science program is practical in the sense that you'll use it all the time in the real world, there are

While not everything learned in an undergraduate computer science program is practical in the sense that you'll use it all the time in the real world, there are a fair number of topics that while not necessary 99% of the time turn out to be the best solution that other 1% of the time. Finite state automata, for example, isn't something I'd bother to learn about but has proven helpful a handful of times.