I wasn't sure what I wanted to study when I started college so I took a lot of Chemistry, Physics, Math, and Compsci classes until I figured out what I wanted. I got a bit past intro classes and learned some stuff that I figured was likely never going to be useful but still had a reasonably good time learning. Some time passed and I made some (very) indie games, and the physics and math studies both paid off very well. I had a good understanding of rotational matrices and was able to calculate casted shadows from dot products and meanwhile wrote a pretty reasonable physics engine. All in all I finally felt like the stuff I'd studied for really no reason and never used paid off.
...Chemistry though? I loved it to death but I've yet to find much of a use for it.