I'm sure we've all had this one. Delivered a Christmas Card that'd been opened (not obviously). Customer says, "My Mum sent the kids a Tenner and you thieving Bastards have nicked it!" after taking the usual deep breath and controlling my natural instinct the twat him I gave him chapter and verse:
"You shouldn't send cash through the post, only cheques or postal orders. And do you think if I had nicked your Tenner I'd be stupid enough to deliver the empty envelope to you?"
He replied, "I'm getting pissed of with this, the same thing happened last year!" And yes I had told him the same thing the year before.

Some people should not be allowed to breed!