After a full year of study, Laugh Lab in UK has determined the world's funniest joke:

“A couple of New Jersey hunters are out in the woods when one of them falls to the ground. He doesn’t seem to be breathing, his eyes are rolled back in his head.
“The other guy whips out his cell phone and calls the emergency services. He gasps to the operator: ‘My friend is dead! What can I do?’
“The operator, in a calm, soothing voice, says: ’Just take it easy. I can help. First, let’s make sure he’s dead.’

“There is a silence, then a shot is heard. The guy’s voice comes back on the line. He says: ‘OK, now what?”’