Short and sweet is nice:
"I got it Coach"...when they are yelling for a call as you are making the call.
"He was displaced Coach"...when they are arguing that it was not a certain foul.
"I might have kicked it Coach"...when you missed an obvious call, or made an obvious bad call.
"Enough Coach"...when you don't want to hear anymore. (Be prepared to back it up...don't keep saying "enough" without consequences)
"Not there" (optional:while shaking head)...when coach is screaming for call such as over and back.
"Spot"...for spot throw-in.
"Watta ya want Coach"...(After whistle and while underhand palm up pointing to coach)...when coach has been granted a time out.
There are many more...but, you get the idea. KISS...Keep It Simple Stupid.
