This might seem like a really strange answer -- but one of the courses that really stuck with me - comparative religion. I was raised by two atheists, and having that exposure to the religions and cultures was invaluable to me. I didn't come out an expert, obviously, but with enough to have a general understanding. That has served me well in my career as I've often been in international roles dealing with people from all over the world. Religion and culture are so intertwined, that having an understanding of religious beliefs and traditions helped me in understanding the diverse people I meet (and continue to meet).