Special agent, a detective or investigator for a state, county, municipal, federal, or tribal government
Agent (law), in commercial law, is a person who is authorized to act on behalf of another (called the principal) to create a legal relationship with a third party
C & F Agent abbreviated from Clearing and Forwarding Agent (India).
Election agent, person legally responsible for the conduct of a candidate's political campaign (UK)
Free agent, sports player whose contract with a team has expired
Literary agent, person who represents writers and their written works to publishers, theatrical producers and film producers
Press agent, professional publicist who acts on behalf of his or her client on all matters involving public relations
Sports agent, person who procures and negotiates employment and endorsement deals for a player or coach
Talent agent or booking agent, person who finds jobs for actors, musicians and models, etc., in various entertainment businesses
Foreign agent, person representing the interests of foreign powers; in the U.S.A., mandated by the Foreign Agents Registration Act to be identified to the American public
Political Agent (Political Resident), an official diplomatic position in British Empire
Patent agent or patent attorney, person who has the specialized qualifications necessary for representing clients in obtaining patents and acting in all matters and procedures relating to patent law and practice
Real estate agent or real estate broker, person who acts as an intermediary between sellers and buyers of real estate
Homo economicus, concept in some economic theories of humans as rational and broadly self-interested actors
As discussed by economists as the principal–agent problem, agent means anyone supposed to act in the interests of the principal, especially insofar as the actions of the agent cannot be completely monitored by the principal. In this sense agent includes such diverse and common roles as auto mechanic, a doctor, a lawyer, an investment advisor, any fiduciary, a contractor, any employee (from the point of view of the employer), and a political representative in a democracy.
Rational agent, entity which has clear preferences, models uncertainty via expected values, and always chooses to perform the action that results in the optimal outcome for itself from among all feasible actions