Here is a quick poll for readers who have chosen to specialize themselves in one or another area of professional practice or study. Firstly, what is the area you have chosen? What made it appealing? Has it worked out the way you expected? Secondly, what different area seems most appealing to you now (whether or not it is actually different from the one you do).
Personally, the non-policy-analysis area that appeals to me most is probably applied biological sciences. If I had the time, money, and inclination to do another university degree, the one that would probably teach me most and be most interesting would be in biology, botany, or biochemistry.