The fundamentals of actuarial science: probability, time-value of money, and tail-risk have absolutely benefited me. I do gripe that much of the material is out-dated. I sat for all my exams within the past 15 years and (for example) we had a lot of option pricing models that have been archaic since the 90's and no machine learning (material has been updated with ML, but it constantly feels a couple decades behind).