What Federal Agency is for Me?

Hello, I am looking into law enforcement as a career, I am interested in the FBI, U.S. Marshals, DEA, and CIA. What I want to know is what is the best job for law enforcement, i want to have a field job, not as much as a desk job. And by field job I mean I want to guard places, guard people, stuff like that. If you know of any job that sounds like that please tell me.