Punch a hairdresser : Get charged with assault
Punch an engineer: Get charged with assault
Punch a gas station attendant : Get charged with assault and attempted robbery.
Punch a cop : Get pepper sprayed, tazed, beaten, shot, and if you survive get charged with assaulting a police officer and resisting arrest.
Punch a Navy Seal : A quick death
Punch a Nurse : Nothing. In fact you can probably get the nurse in trouble if you file a patient complaint form.
Punch a retail worker: The manager will give you a discount, force the person to apologize, and fire them on the spot.