When driving North out of Boonah (S E Qld) there is a huge sign that reads "God can cure hurting marriages - There's Hope!" Some of the local good old boys painted out the word God and replaced it with the word Sex.
I still laugh every time I drive past that sign (even though it was fixed rather quickly).
Funniest sign I ever saw was at a farm gate in NSW, around Christmas time - it was red and white, had a big arrow on it pointing down the driveway, and read: IN HERE YA FAT BAST*RD
BP