So, in addition to statistics, I've been dabbling a little in fractal/chaos theory. Nothing serious, but enough to know that behind even the simplest functions there lies an amazing complex landscape. Who knew that z2+c could be so rich?
At any rate, I did all this stuff back in college, but in specializing I've forgotten most of it (except for the occasional admonition that it's often easy to confuse the complexity of dynamic systems for noise of a stochastic [random] system).
As I get older, it's become easier to lose the wonder. However, beneath every simple surface could be a world of complexity that will inspire a new round of curiosity.