It used to make my Grandfather's day when the Jehovas came calling. He was in his late 90's but could still argue the finer points of theology!! 
I have one of there head church members living across the road from me.
Absolute lovely bloke.
Used to get on great with him and his missus until my missus left me to send out the christmas cards ...............

You can guess what happened and just to make it worse, a few days into the new year he knocked on my door to explain why we didn't recieve a card of them. I (as you do) invited him in for a cuppa (we was watching a dvd at the time)
Much to my horror and I can honestly say it was NOT deliberate we were watching "Life Of Brian" at the time. He stormed out of the house and no amount of apoligys / explanations have made any difference

Oh well, its one lot less to bang on our door