For a prolonged tour in the field, the little things matter just as much as the big things. And nothing is smaller or more easily forgettable than the lowly travel adapter. I picked mine up in an airport somewhere in Japan as an afterthought, like many travelers, once I got to my destination and realized I had no way to charge up my netbook.
The travel adapter seems inconsequential, but choosing the wrong one can be fatal. I got lucky, because the only one in stock turned out to be a workhorse, but horror stories abound of the unsuspecting graduate student plugging their vital equipment into a suspect outlet and frying a computer, blowing a critical sensor, or setting their shack on fire. Electricity is not to be taken lightly.