Le Samouraï (Jean-Pierre Melville, 1967)

Bar owner:
Qui êtes-vous? (Who are you?)

Jef:
Aucune importance. (Not important.)

Bar owner:
Que voulez-vous? (What do you want?)

Jef:
Vous tue. (To kill you.)
____________________________
Call for help in times of danger

“Thief!!” - “Au voleur!”
“Stop / Arrest him!” - “Arrêtez-le!” (or “Arrêtez-la!”, if the criminal is female)
“Help!” - “Au secours!”

To be a cool hitman, you may need...

Hat - un chapeau
Coat - un manteau
Trench coat - un trench-coat
Gloves - des gants
Cigarette - un cigarette