Back in college, I had a class where we built a simple Scheme interpreter in Standard ML. The professor also demonstrated a taste of Haskell. I eventually plugged in to the local functional-programming community, which was into cooler stuff in general, and later got a full-time job working in Scala.

Heavy, inheritance-based object-oriented programming as in 1990s- and early 2000s-style C++ and Java feels tedious and inefficient in comparison.