Mr. & Mrs. Smith (2005)

Overview
Marriage has gotten stale and predictable for John and Jane Smith, an average-on-the-surface husband and wife who don't yet know that they share the same undercover line of work: They're both guns for hire. Hiding their occupations has never been a hardship for either of them until they discover that their next assignment involves them targeting each other. Can they go through with their respective missions, or will love prevail?