There are many synonyms for the phrase "big gun," which refers to someone who is powerful and influential in a particular field or context. Some common synonyms include "heavyweight," "top dog," "big shot," "mover and shaker," "kingpin," "bigwig," "tycoon," "magnate," and "honcho." Each of these terms conveys a sense of authority, skill, and experience, and they are often used to describe people who occupy positions of leadership or influence in business, politics, or other high-profile industries. Whether you are looking for a more subtle way to describe someone's power or simply seeking to change up your vocabulary, these synonyms can help you communicate your thoughts effectively.