Mr&MrsSmith

Boy meets Girl.
Boy and Girl pretend to fall in love.
Boy and Girl are high-priced assassins.
Both, Boy and Girl, think that a family is good cover.
Five or Six years later, Boy and Girl are hired to kill each other.
Between bullets, they fall in love.
Then a bunch of people die in a heavily choreographed shootout.

However you reacted to the trailer is exactly how you will react to the film.

I thought this movie was a lot of fun.