i remember an ad in high times for a drug test 'aid' called Urine Luck
The best unconfirmed ones I've heard are the Arab / Israeli cheese shop called Cheeses of Nazareth and the kebab van in Australia called Jason's Donner Van...
for this festival that i helped organise last summer the sign for the dance tent read:
"now is the summer of our disco tent".
Edit: I heard about a camping/outdoor supplies type shop that was seen with a sign in the window saying "Now is the winter of our discount tents". Puntastic.
Ha ha, that reminds me... there was an outdoors shop near us that once advertised a winter tent sale with "now is the winter of our discount tents".