Chemical engineering and history (dual degree program)
I definitely would have stuck with Chemical engineering, since the engineering education builds important skills well beyond the discipline. However, thinking back, I would have kept history as a minor (not a second degree), which I love, but do a dual degree program with a business major, probably marketing. A few years after undergrad, I went back for a MBA and moved from the R&D side of my industry to the commercial side.
Any major that doesn't end in the word "studies"!