Mechanical Engineering

First of all, I want to say that all programs of mechanical are the best. You have to find your interest. As per your question, I am listing out some branches of Mechanical Engineering, find your interest and get in-depth knowledge of it.
Acoustical Engineering-Concerns the manipulation and control of vibration, especially vibration isolation and the reduction of unwanted sounds.
Manufacturing engineering-Concerns dealing with different manufacturing practices and the research and development of systems, processes, machines, tools and equipment.
Thermal engineering-Concerns heating or cooling of processes, equipment, or enclosed environments.
Vehicle engineering (my favourite one )-The design, manufacture and operation of the systems and equipment that propel and control vehicles. Power plant engineering - Field of engineering that designs, construct and maintains different types of power plants. Serves as the prime mover to produce electricity.
Energy engineering- It is a broad field of engineering dealing with energy efficiency, energy services, facility management, plant engineering, environmental compliance and alternative energy technologies. CAD/CAE - is the broad usage of computer software to aid in engineering analysis tasks. It includes Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), Multibody dynamics (MBD), and optimization.
Mechatronics-Mechatronics is a multidisciplinary field of engineering that includes a combination of systems engineering, mechanical engineering, electrical engineering, telecommunications engineering, control engineering and computer engineering.