Sheket Bevakashah
Hebrew for "Quiet, please."  Well-known to anyone who attended Hebrew school as a child.  Traditional response is "hey!" sometimes accompanied with a raised fist, and always followed by silence.  Used to get everyone's attention so they will settle down and listen.

As used in The Hebrew Hammer.
Speaker: Sheket Bevakashah!

Crowd: Hey!

Speaker: Sheket Bevakashah!

Crowd: Hey!

Speaker: Sheket Bevakashah!

Crowd: Hey!

Speaker: Okay, now that I've got everybody's attention...