Opportunities which require a diversity of skill sets are my favorite. Every day becomes a new day with a new challenge and an opportunity for learning or experiencing something new.
I have migrated through positions requiring various combinations of hardware design, firmware development, software design, network infrastructure management. All have been interesting and rewarding.
Anything having to with integration, systems management, troubleshooting, and development are favorite challenges. Devops, Continuous Integration, Continuous Improvement, Continuous Delivery all fit in with that framework of thinking.