"Leave your brother alone!"
And mostly for Baby (our resident seagull who loves to lurk where there may be a promise of food...):
"Get out. The kitchen is closed!"
I seem to always be
"Can I hear a manner word?"
"Use your words"
"I can't understand you when you're whining" followed by
"Talk like a big boy, please" or "I'm waiting to hear your big boy voice" (Middle is our resident whiner)
"That's not a nice word" (The boyz' favorite "not nice words" are currently: stupid, dummy, balls, poop, and pretty much any sort of bodily function)
"That's not being a good listener" or "Open your listening ears"
Famous punishment phrases: "That's strike one..." (usually) followed shortly thereafter by, "That's strike two" with the follow-up, "One more strike and you're in time-out." And then, of course, "Strike three. You're in timeout Mister. Go sit on the steps until the microwave dings."
So we make it through the day. It's
"Last one up the stairs is a poo-poo platter!"
"Did you kiss your Mother today?"
"Are you my best Big/Middle/Little boy?"
"Good night. Sleep tight. Don't let the bunkbed bugs bite."