I totally agree with wanderer100.. no such thing as high yield topics when it comes to MCAT.. however, if you are asking the question because you are just now starting to study for MCAT physics, and you want to know which Physics topics should you focus on, I would say that would be Electricity and Magnetism, because of the abstract nature of this subject, it takes a lot of time to understand it
I also think Light/Optics and Waves are a "tricky" and may require more attention than other topics