Ideally, working in a sales or consulting role for a company just breaking into a regional market... selling high-tech products for the European market for an American based Tech company that doesn't want to committ to opening an office in Europe.

You would get the flight home to the U.S. (or wherever you live), once or twice a month, all the hotel stays you could ask for, and finally, the internal European flights (almost all in C/J class because the fares are almost no different). Finally, you could even skip one of the flights home every once in a while, keep the ticket and exchange it for some very nice trips to other locations with the girlfriend/boyfriend/spouse/dog/cat, you get the idea

As mentioned, Investment Banking is good. Also, project finance (similar to IBanking)is good, where you go out an evaluate specific projects. It doesn't need to be finance either, as mentioned architecture is good.

Ideally choose a company that wants to do / is doing International business, is small (i.e. doesn't have a lot of dedicated travelling headcount) and is not yet committed to opening foreign offices!