I really think 412 is a great elective. It has flexibility for different requirements, the exams are very fair and straightforward, and you get to learn R code and Tableau. R code is kind of boring but a very useful tool in many different situations, and Tableau is very fun to use.
I agree with Alec. I think ISyE 412 was my favorite ISyE elective I took during my undergrad. I used it as my Quantitative Methods technical elective and I found the class both very interesting and useful. My favorite thing I learned in that class was Tableau. The skills you learn are extremely useful.
Apart from 412, I think 549 is also a good one. It takes human factors engineering into more depth from what you learn in 349. On top of that, Prof. Silber is a really great professor. She knows her students really well.
I agree with previous replies that 412 is a great elective. ISyE 517 was also a great elective if you are interested in the health care field. You learn about how an Industrial Engineer can benefit hospitals using different decision analysis tools.
To fulfill an engineering science credit, I took BSE 367 Renewable Energy Systems. I took it over the summer, and it was a very interesting course. Not only did I learn about the physics and chemistry behind multiple different renewable energy sources, but I also learned about the economics of each source (deciding whether a source is economically feasible). The course was also self-paced with no synchronous lectures. I highly recommend taking this course if you are interested in renewable energy.