coup de main - noun
\ˌkü-də-ˈmaⁿ
Definition of coup de main : an attack that achieves complete surprise.

Anna Kendrick's a cappella cup song live on Letterman.

Anna Kendrick appeared on 'The Late Show with David Letterman' earlier this week in support of her new film, 'Pitch Perfect'.

Check out Letterman giving her a STANDING OVATION below...