These are supposedly actual signs that have appeared at various locations.
Sign in an office: "We shoot every 3rd salesman, and the 2nd one just left."
Sign in a veterinary's waiting room: "Be back in 5 minutes. Sit! Stay!"
Sign on music teachers' door: "Out Chopin."
Sign at the electic company: "We would be delighted if you send in your bill. However, if you don't, you will be."
Sign in beauty shop window: "Dye now!"
Sign on a garbage truck: "We've got what it takes to take what you've got."
Sign at a computer store: "Out for a quick byte."
Sign on restaurant window: "Don't stand there and be hungry. Come in and get fed up."
Sign in a bowling alley: "Please be quiet. We need to hear a pin drop."