The answer to this question is only limited by your imagination. However, here are some of the most commonly found uses for the practice of dowsing:
Finding water or precious metals
Finding anything buried underground e.g. pipes, cables, graves, ruins etc
Accessing information e.g. health information, decision making, supplement choices
Uncovering earth energy lines and other geomantic features in the landscape
Finding lost items, people or pets
The list really is endless!