According to this site
res://Www.laughlab.co.uk/summary.html
This the funniest joke ever

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?"

this is good one but I think this story about email which went to wrong wife is a bit better