What "aspect" of hacking do you believe is most enjoyable (and useful for potential employers) to have researched?

Experienced hackers (or people working in ethical hacking) what subject do you think seeing someone with 'good knowledge' of the subject would fascinated / please you most to see? what "skill set" they would look for in an accomplice / future employee.

I ask this as I wish to create a detailed report to help me with future employment. I can reference this, and (hopefully) employers will be pleased to see someone with this specific knowledge! Thank you for your time.