In the United States, the term John Q. Public is used by law enforcement officers to refer to an individual with no criminal bent, as opposed to the terms perp or skell, used to qualify unsavory individuals.
Similar terms for the common family can be Mr. & Mrs. John Q. Public, Mr. & Mrs. John Q. Citizen, or Mr. & Mrs. John Q. Taxpayer
Roughly equivalent, but more pejorative, are the names Joe Six-pack, Joe Blow, and Joe Schmoe, implying a lower-class citizen (from the Yiddish schmo: simpleton, or possibly Hebrew sh'mo: (what's)-his-name).
The equivalent in the United Kingdom is Joe (or Jane) Public, Joe Bloggs, Tommy or Tommy Atkins is the generic soldier's name there. The phrase "Tom, Dick & Harry" is often used usually to indicate possibly unwelcome people as in the phrase "any Tom, Dick and Harry could have..." walked in, picked that up, etc.
The historical and legal equivalent is the man on the Clapham omnibus, although this is a generic description rather than a generic name.
In Australia, John (or Jane) Citizen is usually seen as a placeholder in credit card advertisements, while Joe (or Jane) Bloggs is commonly used in speech. Joe Blow is also in common parlance in Australia, but contains slight overtones of inappropriateness. For example, in the admonishment: "You left the door unlocked and any Joe Blow could have walked right in"