Select best elective out of these for employability

I would probably point out Cloud computing or Big Data. While you may not be able to put them on the resume, you can use the knowledge and background in conversation/interview and be a stronger candidate. Many people know what these kind of but don't really understand what it entails (e.g. Cloud computing is great but once you load the data in the cloud, you are stuck paying for it in perpetuity). Big data is great too but most companies cannot use and have no way of leveraging it.

Both areas are high growth industries. Another skill I would recommend is public speaking or presentation skills or excel modeling - those are always in demand and never get old.

Finally, if you can get a Project Management certification or experience, it is very handy as every knows - good project managers are hard to find.