Maybe this isn't that obscure, but I find it funny that it is actually a criminal offense:
TITLE LXII
NH CRIMINAL CODE
CHAPTER 645
PUBLIC INDECENCY
Section 645:3
645:3 Adultery. – A person is guilty of a class B misdemeanor if, being a married person, he engages in sexual intercourse with another not his spouse or, being unmarried, engages in sexual intercourse with another known by him to be married.
TITLE LXII
NH CRIMINAL CODE
CHAPTER 645
PUBLIC INDECENCY
Section 645:3
645:3 Adultery. – A person is guilty of a class B misdemeanor if, being a married person, he engages in sexual intercourse with another not his spouse or, being unmarried, engages in sexual intercourse with another known by him to be married.