What is the most common type of lawyer?

Common to who?

Common everyday people are probably most familiar with family law, probate, personal injury, and criminal defense.

Movie stars are probably more familiar with Agent Representation (not sure what they call it) and contract law.

Big Business executives find their lawyers are more commonly corporate lawyers, tax lawyers, mineral rights, etc

Every facet of life has its lawyers. The key is to figure out what you enjoy, and what you are good at, and go from there!

There's no "most common" lawyer. One of the things you learn in law school is to identify and develop your specialty. Even if you're interested in one particular area, you'll still be exposed to some other areas- as a real estate attorney, I often touch on corporate governance, tax issues and franchise items, and I considered none of those areas until I found out I needed to develop knowledge about them.