Good question. I think there are 3 considerations you need to keep in mind, as you evaluate the choice of a major:

1) I see college as more of a preparation of a person for life than necessarily as a training school for a job, though it certainly will help to orient and guide one. If this is so, I would think that a helpful background for ministry or missions would be in the humanities, and probably as broad a selection as possible. Fields such as history, literature, psychology, anthropology (especially cultural anthropology), and perhaps even sociology prepare you to understand people, where they are coming from, and their basic ideas and needs. Particularly if you plan to go on to graduate school - either to a seminary or a more specialized M.A. level degree - I would encourage you to pick a major in one of the above fields, take the minimum courses required, and then take lots of electives in the other fields.

My associate, a recent college graduate and the son of a missionary, upon reading my answer suggested the following: "a course in philosophy, art history (esp. non-western), cultural geography, political theory, macro-economics, urban theory or literature in translation from a different civilization. I don't want to overwhelm her, but I thought specifics might underscore the main point: Breadth of Inquiry."

2) A second consideration would have to do with you as a person. What are your interests? What really turns you on? Developing and deepening your knowledge in this area may well prepare you for your future work. "Ministry" and "Mission" are broad fields. Exploring your interests in depth may well prepare you for the unique place God has made you for and is continuing to prepare you for.

3) A third, and often neglected, aspect would have to do not so much with a "major" as "exposure" as part of your preparation. I would strongly urge you to make friends with people who are different from you (other races, other cultures), participate in a mission trip, and get involved in ministry on campus. Learn how to develop your own spiritual life, how to share the Gospel, how to answer the tough questions, and how to help a new Christian grow. These are skills you'll be able to use all your life and there is no better place to learn them than right where you are! I'd encourage you to move into the dorms or some other incarnational evangelism position, where you can actually live with people you might not have chosen to be your friends, but can learn from them about where other people come from.

May the Lord guide you as you continue to respond to His call, and make you a blessing to many all your life.

Jack