I did my undergrad in Mechanical engineering, hence I can speak a bit on that. Mechanical engineering is considered as the mother branch of engineering. It has various disciplines such as Design, Manufacturing, and Thermal. The thing I like about mechanical engineering was that you would first start with introductory courses on all these various disciplines and if you decide to like one, you can further advance your knowledge by taking more advanced courses. Even when it comes to a job, you can pick and choose based on your interest in these disciplines.
One thing I would say was how fantastically mechanical engineering has adopted computer technology over the past few decades, which brought a revolution in this field. So even if you are interested in pursuing mechanical engineering, be sure to have a good working knowledge of Computer Science as you will be able to make wonders.