My favorite non-ISYE class so far has been CS200. It certainly was challenging learning Java from scratch. However, I think the programming knowledge gained will far outweigh the amount of stress that the class created.
My favorite non IE class was econ 101 with David Johnson. He was so energetic and made the already interesting topic very enjoyable to learn. I would strongly recommend taking this with Johnson if you have the opportunity.
For my CS elective, I’m currently taking a new Data Programming class! CS320 is the continuation of CS220 which is a programming class on Python. I think it’ll be very useful for IEs since a lot of new analytic and decision-making tools revolve around Python and data programming. The projects are super fun and relevant, and the current professor is a great teacher.