These are the kinds of signs I'd make, just so I could see the reactions of people reading them.

Spotted in a toilet of a london office:
Toilet out of order. Please use floor below

In a laundromat:
Automatic washing machines: please remove all your clothes when the light goes out

In a london department store:
Bargain basement upstairs

In an office:
Would the person who took the stepladder yesterday please bring it back or further steps will be taken

In an office:
After tea break, staff should empty the teapot and stand upside down on the draining board

Outside a secondhand shop:
We exchange anything - bicycles, washing machines, etc. Why not bring your wife along and get a wonderful bargain?

Notice in health food shop window:
Closed due to illness

Spotted in a safari park:
Elephants, please stay in your car

Seen during a conference:
For anyone who has children and doesn't know it, there is a day care on the first floor

Notice in a field:
The farmer allows walkers to cross the field for free, but the bull charges

Message on a leaflet:
If you cannot read, this leaflet will tell you how to get lessons

On a repair shop door:
We can repair anything. (please knock hard on door - bell doesn't work)