The phrase "little guy" is often used as a term of endearment or to describe someone who is physically small in stature. However, there are a variety of synonyms that can be used in its place, each with their own unique connotations. For instance, "small fry" or "peewee" can be used to refer to children, while "underdog" or "David" might be used to describe someone who is facing a difficult challenge. "Pipsqueak" and "runt" are more derogatory terms that suggest weakness or insignificance. Ultimately, the choice of synonym depends on the context and the desired tone of the conversation.