Funniest was a rude one - my wife and I were sat in front of the computer waiting for a member of my family to log on one Christmas day. We got a request for a meeting, said yes, and up popped a naked man onto the screen.
We both recoiled and shouted "Urgh!" forgetting that the microphone was on. He disconnected quite quickly!
Vile at the time, but funny looking back!
Sorry, I know you said nothing rude, but I took that to mean no explicit mentions of rude displays rather than rude subject matter!